Welcome to Observatory

When you first open Observatory, you’ll see its welcome window pop open. It lets you quickly access this documentation, open an existing Observatory library, or create a new library. Creating a new library is what you want to do if this is the first time you use Observatory. Just click the New button.

Welcome window
Welcome window

A new window will pop open with your new untitled Observatory library document. This window is where you’ll do all of your work. You can create as many library documents as you wish. Observatory is not limited to a single library, and you can have multiple libraries open at the same time.

Before diving in, let’s take some time for a quick overview of Observatory’s user interface:

Empty new library window
Empty new library window
  1. Toolbar – Along the top of Observatory’s library window you’ll find a row of useful buttons in the Toolbar. Fully customizable the Toolbar makes it easy for you to switch between the different view modes, the Virtual Observatory, show the image download progress and a whole lot more. See Using the Toolbar for more details.

  2. Sidebar – Along the left side of Observatory’s window is the Sidebar. Fully collapsible, the Sidebar provides an outline view of all the albums, smart albums and folders in your library, an outline view of all source folders, and image previews. To learn more about the Sidebar, see Using the Sidebar.

  3. Unless created by dropping a Finder folder on Observatory’s application icon, initially an Observatory library does not contain any images. To help you quickly import a folder of images, click the Import Images… button in the center of the window. If you want to be more selective, click Add Source Folder… first. Lastly, if you wish to search for and import research images from the archives of professional observatories, just click the Virtual Observatory button instead. After you have imported one or more images, you can use the Toolbar to switch the window’s center contents between:

    • Browser – The Browser displays the images of the currently selected album, smart album or folder in your library. There are three kinds of Browsers. To learn more about them, see Using the Browser.

    • Editor – The Editor shows the image you have currently selected in the Browser in all its glory, or more specifically since you can have multiple images selected at once, the one that has the focus. The Editor can be shown at the same time as the Browser, or without it. Observatory also lets you display multiple editors at once. Using the Editor has more details about the Editor.

    • Virtual Observatory – The Virtual Observatory gives you direct access to 10+ professional archives and download research images from ESO, Keck, Gemini, Palomar, Hubble, Spitzer, WISE, 2MASS, SDSS and more. You can search for images by name and equatorial coordinates, optionally with help of the SIMBAD and NED astronomical databases. You can learn move about the Virtual Observatory in Using the Virtual Observatory.

  4. Inspector – Along the right side of Observatory’s window are the Inspectors. Fully collapsible and consisting of the Image Version, Layer Adjustment, Measure, Stack and Album inspectors, as well as inspectors for attachments, channels, layers and the histogram, it provides access to most of the tools for adjusting selected images and their meta data. For more details about the Inspectors and what each of them does, see the Using the Inspectors section in the documentation.

Getting Started

To get to know Observatory, start with a library for a single target object and a limited number of images, e.g. 5 bias, 5 dark and 5 flat images, all optional, and 5 light images.

We regularly add videos to our website that demonstrate certain aspects of Observatory. This includes calibration, stacking, plate solving and how to find images with Virtual Observatory. Choose Help ▸ Videos to see them.

Create or Open a Library

Create a new empty library by clicking the New button in the welcome window, or choose File ▸ New Library in the main menu. Open an existing library by choosing it in the Open Recent menu of the welcome window or main menu, by clicking the Open… button in the welcome window or choosing File ▸ Open… (⌘O) in the main menu.

Alternatively, click and drag the Finder folder containing the target object’s images and drop it onto the Observatory application icon. This creates a new library and immediately imports the images.

Import Images

When you import an image into an Observatory library, it stores a reference to the image, and extracts its meta data (dimensions, exposure date/time, exposure duration, etc). Observatory never copies, moves or alters this master image.

If you want to import a folder of images into a library, choose File ▸ Import ▸ Images… (⇧⌘I), select the folder and click Import.

You can only select and import individual images into a library if you have given Observatory permission to access their containing folder. Choose File ▸ Import ▸ Add Source Folder…, select the folder and click Add Source Folder. Then choose File ▸ Import ▸ Images… (⇧⌘I), select the individual files and click Import.

Notice how FITS, XISF and SBIG images are displayed with actual thumbnails and previews in the Import Dialog and in the Finder. Observatory includes Quick Look generators to accomplish this feat, as well as Spotlight importers for helping you find images with Spotlight. Select any image in the Import Dialog or Finder and press spacebar to quickly see it up-close.

Put your bias, dark, flat and light images in appropriate albums. You may put them all in a single album, or organize them in multiple albums. Select the images, and choose Image ▸ Move to New Album. Make sure to put related images that you intend to stack in the same album. You can have multiple stacks in an album.

View Images

After importing images into a new Observatory library, their thumbnails are displayed in the Image Browser. The thumbnail size can be adjusted by the slider in the Browser Bar towards the bottom of the Browser.

Browser Bar
Browser Bar

To view an image in more detail, double click it. Alternatively, select it and choose View ▸ Show Browser & Editor (⌥⌘⏎), or click the corresponding button in the Toolbar.

Show Browser & Editor
Show Browser & Editor

Instead of only displaying the Browser, Observatory will then display the Browser together with the full image in the Editor.

Choose View ▸ Editor ▸ Assistant, or click the button in the Toolbar, and select another image while pressing the option key. This image will then appear next to the other image. Choose View ▸ Editor ▸ Focus Next Editor (⌥⌘`) to switch between them, or click their title bar in the Editor.

Assistant Editor Toolbar Button
Assistant Editor Toolbar Button

Choose View ▸ Editor ▸ Standard, or click the corresponding button in the Toolbar to switch back to a single editor.

Create Calibration Masters

Select the bias images and choose Stack ▸ Stack. This creates a single, stacked image from the selection. Select the stack and use the Stack Inspector towards the right of Observatory’s library window to change how the images are stacked, e.g. Average (the default) or Median. Do the same for your dark and flat images.

Stack Inspector
Stack Inspector

The stack image of a stack is not like a regular image on disk, but generated dynamically. To do any further processing of it or use it as calibration image, a snapshot must be created. Select the bias, dark and flat stacks, and choose Image ▸ New ▸ Master.

Select the new master image of the bias stack that you have just created, and choose Image ▸ Move to Album ▸ Bias Calibration. This moves it into the library’s master calibration album and adjusts its image type accordingly. Being in this album makes the master bias calibration image available to the Calibrate Adjustment you will use later.

Do the same for the dark and flat images, moving the master dark by choosing Image ▸ Move to Album ▸ Dark Calibration and the master flat by choosing Image ▸ Move to Album ▸ Flat Calibration.

Calibrate

Select the light images and choose Layer ▸ Calibrate. The Layer Adjustment tab towards the right of the window will now display the Calibrate Adjustment inspector.

Calibrate Inspector
Calibrate Inspector

Select the master bias, dark and flat in this inspector. The inspector only lists the calibration images relevant to your selection. It displays only those that have the same dimensions, and also takes exposure time, CCD temperature (if set) and filter name into account. If it doesn’t display the expected calibration images, check if this information matches with your light images.

Stack

Select the light images and choose Stack ▸ Stack. Select the stack and then choose Average (the default) or Median in the Stack Inspector.

With the stack still selected, choose Stack ▸ Focus on Stack (⌃⌘[), or click the button in the Focus Bar.

Focus Bar: Focus on Stack
Focus Bar: Focus on Stack

Observatory will now display the stack’s comprising images. The center of the Focus Bar has three buttons that allow you to quickly select the stack image (the result of stacking the images), the stack’s current pick image, or all images in the stack, respectively.

These three buttons can also be used in combination with the option key and the Assistant Editor. For example, you can use them to quickly display the stack image in the right-hand side editor, and individual images in the left-hand side editor during stacking.

Align

Aligning images in a stack is always relative to the stack’s pick image. Typically, the pick image is the best or most representative image in the stack. Initially the pick is the earliest exposed image in the stack, but you can change it by selecting another image and choosing Stack ▸ Pick (⌃⌘8).

Select all images in the stack by choosing Stack ▸ Select ▸ All Items or clicking the button in the Focus Bar.

Choose Layer ▸ Stack ▸ Align.

This adds an Align Adjustment to each image, in addition to the Calibrate Adjustment. After processing has completed, the images will be aligned with the pick image, and the stack image is updated.

Align Inspector
Align Inspector

With all images still selected, click the “play” button in the Editor to quickly inspect the alignment. It changes into a “pause” button during the blink animation. Click it when done.

Blink Selection
Blink Selection

Now choose Stack ▸ Unfocus (⌃⌘]) or click the Unfocus button in the Focus Bar.

Export

Select the calibrated & aligned stack image and choose File ▸ Export ▸ Image… (⇧⌘E) to export it in the desired format. Observatory has powerful folder and file naming template support, but for now just select None as Folder Format, Name as Name Format, and click the Export button.

Plate Solve

Select the calibrated & aligned stack image, and choose Image ▸ New ▸ Master. For a regular image you can skip this step.

Choose Image ▸ Match… (⌃⌘M), then enter the name of the object in the image, and click Match All.

After a few seconds, the image will be plate solved and a badge icon appears on the image thumbnail.

If Observatory is unable to plate solve the image, choose Image ▸ Match… again and click the triangle to expand the match settings. Make sure that the pixel scale is fairly accurate. For large detectors the image may be distorted near the corners, and the frame size setting should be reduced. For noisy images increase the detector sensitivity setting.

Choose Overlay ▸ Show All Overlays to display the equatorial grid, scale, Messier, NGC/IC and other overlays on the image.

In addition to relating image pixels to sky coordinates, Observatory’s plate solver also automatically tags the image with data from its object database. You can then more easily find the images in the Browser by using its search field, or rely on the predefined Smart Albums in the Objects folder of the sidebar.

Virtual Observatory

At any time you can choose View ▸ Show Virtual Observatory (⇧⌘F) to search the archives of professional observatories for research images. Enter the target’s object name, identifier or coordinates and click Search. You can filter the search results, or by expanding the Preview panel in the sidebar see image previews before downloading the FITS images. Move the mouse cursor over the preview and click the Quick Look button to see a larger preview image. Click Import to download the FITS image into the Observatory library.

Alternatively, select the plate solved image, press the option key and choose View ▸ Match Virtual Observatory (⌥⇧⌘F). This initiates a search in the archives using the center coordinates of the image.

Save the Library

For checking the quality of your images during or after an observation session there is no need to save the library afterwards, but usually you would save it. Choose File ▸ Save… (⌘S) and enter the name of your library (e.g. “Observatory Library”), and its location. Lastly click the Save button.

What’s in a Library

Observatory Library
Observatory Library

An Observatory library is a document package – an ordinary folder that is presented by macOS Finder as a single file. To gain a better understanding of what Observatory does with your images, lets take a high-level look at what is inside a library.

A library may contain the following folders:

  • Attachments

    Observatory allows you to attach files to images and albums. You can for example attach an observation log or research paper to an album, to quickly look into or open it while working in Observatory. Usually you would link the attachments, but you can also decide to embed them in the library, in which case they end up here.

  • Notes

    This folder contains the notes of your images and albums. These notes are extracted automatically from your images when you import them (e.g. FITS COMMENT and HISTORY keywords), but you can also add your own.

  • StoreContent

    This folder contains the main database of an Observatory library.

  • Masters

    This folder contains the original files you downloaded using Virtual Observatory as well as the managed masters you created when choosing Image ▸ New ▸ Master.

    After they have been created, none of these files will ever be altered. Only if no image version refers it they are deleted. They are off-limits for the Image ▸ Show Master in Finder and Image ▸ Open Master menu items. You need to choose one of the File ▸ Export menu items if you wish direct access to these files. This is by design, because by enforcing immutability, Time Machine integration is much more space efficient, and you can be certain that data obtained through Virtual Observatory is unaltered.

  • Versions

    This folder contains many small (~ 1 KB) files, one for each image version, that contain metadata. They are usually accompanied by a few helper files.

When you import an image into a library, Observatory doesn’t copy the image, but extracts the metadata (dimensions, exposure date/time, exposure duration, etc), normalizes it, and stores it in the library’s database. It does this for many different types of images, including FITS, XISF (PixInsight), SBIG, DNG, NEF, CR2, TIFF, JPG, etc.

It stores this original normalized data, but also creates a first “version” of it, which is what you see and can edit in the Inspectors.

Key is that it doesn’t copy the actual pixel data of the image. It only maintains a reference to the original file. This master image is not copied, moved, or altered. It remains external to the library. The file reference is stored such that renaming or moving the master file on the same disk will usually not break the link. And if the link is broken, then you can choose Image ▸ Locate Master… to fix it.

Copying a version also doesn’t copy the master image, but only the much smaller metadata. It is therefore a very efficient operation. Changes applied to an image always are applied to a version. For example, if you rotate an image in Observatory, it doesn’t actually rotate the master image, but only adds a “prescription” to the image version.

This approach means that you can for example create one –90° rotated version of a master image, and other +90° rotated version of the same master image, and it would barely use any additional disk space. Or, you can use one version of a master image with a certain weight in one stack, and another version of the same master with a different weight in another stack.

The main difference between a master image and a managed master image, is that the former lives outside the library, while the latter is stored inside the library. A second difference of course is that a managed master cannot be altered, but by using an external editor you can alter a regular master. Observatory does detect if you do alter a master, and allows you to quickly synchronize the metadata using Image ▸ Reset Attributes….

Using the Toolbar

Along the top of Observatory’s window is the Toolbar. Packed with buttons and fully customizable the toolbar makes it easy for you to collect and organize astronomical images.

Toolbar
Toolbar

At opposing ends of the toolbar, you’ll find buttons for hiding and showing the Sidebar and the Inspectors. Above those, you’ll find the standard macOS window controls for closing or minimizing the window or entering Full Screen mode.

At the center of the toolbar along the top, you’ll see an Observatory library document icon and its filename. If you hold down the Command key (⌘) and click that icon or filename, you’ll get a tiny menu that shows you where the file is stored on your Mac. This is sometimes handy for when you’re working on duplicated files and you can’t remember where you saved the last revision. Another use of the document icon is that you can drag it to the Desktop or a Finder window to create an Alias to the file.

To the right of the filename is a small chevron. Clicking it opens a small popup window, in which you can change the name of the file, add tags to help make the file easier to find using Spotlight, move the file to another location on your Mac, or even lock/unlock it.

Filename
Filename

Most of the items in the toolbar have corresponding items in the main menu and are described in more detail in other parts of the documentation.

Stopping Tasks

If the Stop Tasks toolbar button is enabled, Observatory is loading, processing or stacking images in the background. These tasks may be running because you selected one or more images or are adjusting them. Observatory itself can also initiate automatic library maintenance tasks, for example to generate a thumbnail of an image or stack.

Use this button or choose File ▸ Stop Tasks… (⌘.) to gracefully stop image loading, processing and stacking. This will deselect the currently selected images, and also stop the automatic library maintenance tasks. In addition, it will temporarily block Observatory from initiating any new library maintenance tasks.

User initiated tasks always have a higher priority than library maintenance task, and they will gracefully pause them. If a library maintenance task is active while you initiate a new task, that maintenance task will first be completed though. If it is a lengthy one, and you don’t want to wait for it to complete, then use this button to stop it gracefully.

Customizing the Toolbar

To hide the toolbar, choose View ▸ Hide Toolbar or Control-click on the toolbar and select Hide Toolbar. Alternatively you can also just press ⌥⌘T. Repeat this to show it again.

To customize the toolbar, choose View ▸ Customize Toolbar or Control-click on the toolbar and select Customize Toolbar. When you do, a sheet slides down from under the toolbar, revealing a slew of function-related buttons that you can drag up to the toolbar. When you’ve finished making changes to the toolbar, click Done.

Customizing Toolbar
Customizing Toolbar

If you don’t like the changes you’ve made, or if you ever want to reset the toolbar to its default set, all you need to do is drag the bottom row up to the toolbar and then click Done to save the changes. The changes you’ve made to the toolbar are saved along with Observatory’s preferences, so that you’ll see the same toolbar options with every library document you create.

Along the left edge of Observatory’s window is the collapsable Sidebar. The Sidebar lists the image collections in the Library Navigator along with the Preview and Source Folder panes. Near the bottom of the Sidebar, you’ll also find a Search field that makes it easy for you to sift through your collections and find the information you’re looking for.

Sidebar
Sidebar

The Sidebar is open by default, but you can hide and show it again by choosing View ▸ Sidebar ▸ Hide/Show Sidebar (⌘0), or by clicking the Sidebar button in the toolbar.

If you mouse over the right edge of the Sidebar, you’ll notice that the mouse pointer changes to a resizing handle. Click and drag the resizing handle to resize the Sidebar.

The upper half of the Sidebar displays the image collections in your library in a scrollable pane. These collections consist of Folders, Albums and Smart Albums:

  • An Album is a type of container in the Observatory library document that may contain images and stacks of images.

    If you select an Album in the Library Navigator while the Browser is visible, you will see it display all images of that album. The Browser may apply some rules to what is exactly shown, e.g. only those images that have not been manually rejected, or only certain calibration images, but what is displayed are images of the selected album only. Albums cannot be nested.

  • A Smart Album is a dynamic album used to organize images by gathering them based on search criteria. For example, every Observatory library automatically contains a Smart Album named “Globular Clusters”. It returns all images that contain the tag gc. You can also create your own Smart Albums, e.g. to return all images of Planetary Nebulae that were taken through an Ha filter and exposed for at least 20 minutes. Smart albums cannot be nested.

  • A Folder is a type of container in the Observatory library that is used to organize albums and smart albums. Folders can be nested. If you select a Folder in the Library Navigator while the Browser is visible, it will display all images of all albums and smart albums in that folder and its subfolders, after applying the above mentioned rules.

In this Library Navigator, items with children have a disclosure triangle on the left edge. To view the children, click the disclosure triangle to flip open the list. Option-click a disclosure triangle to open or close all of the items within.

The Library Navigator is organized in two parts:

  • The collapsible Library group of the Library Navigator contains predefined Folders, Albums, Smart Albums and other special system generated collections:

    • Inbox

      The Inbox contains all images that have not yet been organized in albums. Organize your images using Image ▸ Move to Album and Image ▸ Move to New Album. Some features of Observatory, like Stacking, are not available for images that still reside in the Inbox, hence you are encouraged to organize them. This makes it also easier to find them back later.

    • Calibration

      The Calibration folder is used by the Calibrate Layer Adjustment. It contains your master calibration images organized in three subfolders: Master Bias, Master Dark and Master Flat. Each of these three subfolders contains Smart Album “Other” and a single Album: Bias Calibration, Dark Calibration and Flat Calibration, respectively.

      You can move a master calibration image to one of these three Albums by choosing Image ▸ Move to Album. When added to any of these albums, its Image Type is forced to “MasterBias“, ”MasterDark“ or ”MasterFlat" respectively.

      Before adding images to these Calibration Albums, make sure that their exposure date, CCD temperature, exposure duration and filter name have been set correctly. This information is used for listing them in the popup menus of the Calibrate Layer Adjustment. For example, if you add a Calibrate Layer Adjustment to an image that was taken with a CCD temperature of –25℃, the popup menus will only list calibration images that were taken at a temperature between at –25.5℃ and –24.5℃.

      The “Other” Smart Albums of the Calibration subfolders contain all images that have their Image Type set to “MasterBias“, ”MasterDark“ or ”MasterFlat" respectively, but which are not in the corresponding Calibration Album.

    • Imports

      The Imports folder contains Smart Albums for displaying all Today’s imports, Yesterday’s imports, all imports of the current week, as well as one for all imports of the current month.

    • Favorites

      If you mark one of your own collections as a favorite by choosing Album ▸ Add To Favorites, it will be added to this item in the Library Navigator. All the collection’s images will implicitly be marked as favorite, including those you will add later. If you wish to mark a single image as favorite, you should choose Image ▸ Add To Favorites instead. For images that are not part of any album, an Inbox item will appear in the Library Navigator.

    • Archive

      When you archive one of your collections by choosing Album ▸ Move to Archive, it will disappear from the Albums section of the Library Navigator, it stops being discoverable using the Library Navigator search field and makes it invisible to Smart Albums. All archived collections can be found under the Archive item.

      Archived collections are not implicitly locked, and can be used like any other collection. They cannot be marked as Favorite though. To unarchive a collection, select it and choose Album ▸ Put Back.

    • Trash

      When you choose the Album ▸ Move to Trash or Image ▸ Move to Trash menu items, the collections and images are not permanently removed from the library right away. You can still restore them by choosing Album ▸ Put Back or Image ▸ Put Back. They are only permanently removed if you choose File ▸ Empty Trash…. For images that are not part of any album when you move them to the trash, an Inbox item will appear in the Library Navigator.

    • All Images represents all images in your library. If you select it while the Browser is visible, you will see it display all images in your library. The Browser may apply some rules to what is exactly shown, but it will do so for the images of all your albums combined, except those that are archived or in the trash.

    You can collapse the Library group by clicking the word “Hide”, which will appear at its right hand side if you move the cursor over it.

  • The collapsible Albums group in the Library Navigator contains all the folders, albums and smart albums that you create yourself. When you first create a library, one folder is created for you:

    • Objects

      The Objects folder contains a large number of default Smart Albums, organized in Folders. Each of them is a filter for a specific tag:

      Smart Album Name Tag
      Asterisms asterism
      Binary Stars **
      Comets comet
      Constellations constellation
      Dark Nebulae dn
      Dwarf Planets dpl
      Emission Nebulae en
      Exoplanets xpl
      Galaxies g
      Galaxy Clusters cg
      Globular Clusters gc
      Meteors meteor
      Minor Planets mpl
      Moon moon
      Open Clusters oc
      Planetary Nebulae pn
      Planets pl
      Quasars qso
      Reflection Nebulae rn
      Sun sun
      Supernova Remnants snr
      Variable Stars v*

      You can use these tags with your own images to make them discoverable in your library. For images that are Matched, i.e., images for which Observatory can relate image pixels to sky coordinates, Observatory adds some of these tags automatically. The Objects folder is initially locked, but you can modify its contents in any way you want by unlocking it.

You create a new album by choosing Album ▸ New Album. Alternatively, you can select a few images, and choose Image ▸ Add to New Album (press to see this menu item). Albums you create can be moved around and into folders, which can be created by choosing Album ▸ New Folder. You can also drop an Album onto another Album, in which case they will be merged. To create a Smart Album, choose Album ▸ New Smart Album.

The Library Navigator’s contextual menu, displayed by holding the Control key while clicking, provides quick access to these and other handy menu commands.

You can accentuate a collection in the Library Navigator by assigning a color label to it with the Album Inspector. There you can also add Tags, assign a Rating or Status to it. In addition, you can add notes and attachments to your own collections. When you do not want any further modifications to a collection, lock it by choosing Album ▸ Lock, or use the lock button in the Album Inspector.

Sometimes you may have created a library for which you are not interested in certain default collections. For example, if your library only contains fully calibrated images, you may never even use the Calibration folders. You can hide them by selecting the collection in the Library Navigator, and choosing Album ▸ Hide Folder. Similarly you can hide Albums and Smart Albums.

To temporarily show the hidden collections, choose Album ▸ Show Hidden. The ones that are marked as hidden will be shown in gray. You can permanently show them once again by choosing Album ▸ Unhide Folder, or the equivalent for Albums and Smart Albums.

Searching Within the Library Navigator

If you have many collections in your library, you might need some help finding the one you are looking for.

At the bottom of the Library Navigator, you’ll see a search field with a little magnifying glass icon in it. After you have clicked it, the Library Navigator will display only those collections that match the search criteria with every character you type . You can search by collection Name, Tag or Status. Or you can search for any of them, which is the default.

To clear the search field, press Escape or click the little Clear search button at its right edge. When you’ve finished searching, the Library Navigator reverts back to its former state of showing you everything.

Near the bottom of the Sidebar, below the Library Navigator, is the Preview panel. It has a disclosure button at its left which, when clicked, reveals and hides the panel. The click area actually covers the whole panel’s title bar, so you don’t have to be too accurate when clicking. Alternatively you can choose View ▸ Sidebar ▸ Show/Hide Preview.

If you are using the Virtual Observatory, and select a search result that is marked with a ● symbol, revealing the Preview panel will have it automatically download a preview image and display it. Likewise, if you select an image in the Browser, the Preview panel will contain a small preview of that image. This is especially useful if you are using the List Browser.

If you want to have a closer look at a preview image, just move the cursor over it and click the Quick Look button that appears. This is especially useful for Virtual Observatory previews, since they are not restricted in size.

You can use the Quick Look window to open the preview image in other applications, for example the Preview application. If you wish to keep it or modify it, please Duplicate it first, because the original preview image may be removed while you use Observatory.

At the bottom of the Sidebar, the Source Folder panel is located. It has a disclosure button at its left which, when clicked, reveals and hides the panel. The click area actually covers the whole panel’s title bar, so you can click anywhere in it to show or hide the panel. Alternatively you can choose View ▸ Sidebar ▸ Show/Hide Source Folders.

A source folder represents a folder in the file system, outside of the Observatory library. Because the macOS Sandbox restricts access to the file system, it is up to you to explicitly give Observatory permission to access the folders in which your images reside, by choosing File ▸ Import ▸ Images… (⇧⌘I) or File ▸ Import ▸ Add Source Folder…. The Source Folder Panel keeps tracks of these folders. Neither these folders, nor their contents, is ever modified by Observatory.

If you choose File ▸ Import ▸ Add Source Folder…, the selected source folders, and optionally all their subfolders will be added to the Source Folder Panel. No images will be imported. Only the source folders are made available to Observatory. If you then choose File ▸ Import ▸ Images…, you will be able to select individual images in these source folders to import into Observatory.

If you skip the File ▸ Import ▸ Add Source Folder… step and choose File ▸ Import ▸ Images… directly, your selected source folders will also be added, and optionally all their subfolders, but also all their images will be imported. So importing images can be done in a single step, but that has the restriction that you will not be able to select specific images for importing.

You can make Observatory unaware of a previously added Source Folder by choosing File ▸ Import ▸ Remove Source Folder…. Be aware that the images in your library that originate from that Source Folder will also be removed, without moving them to Trash first. Your master images in the file system will not be affected of course.

The Source Folder Panel action popup menu provides quick access to these and other handy menu commands.

Using the Browser

Show Browser Only
Show Browser Only

After you have imported one or more images into a library and choose View ▸ Show Browser Only (⇧⌘⏎), or click the first of the four View buttons in the toolbar, the center of its window will be replaced by the Browser .

Image Browser
Image Browser

The browser displays the images of the currently selected collection in the Sidebar. It may apply some rules to what is exactly shown, e.g. only those images that have not been manually rejected, or only certain calibration images.

You can drag & drop images from the browser to albums in the library navigator to organize your images. Currently you can only move images to the albums in the Albums section of the library navigator this way, not the Library section. In addition, you can drag & drop images and stacks on top of another image or stack of the same album. This combines them in a stack. In both cases, if you press the option key while dragging, the image version is copied instead of moved. Also, the browser cannot be focused on a stack for any of this to work.

There are three types of browsers. Choose one of the View ▸ Browser menu items to switch between them, or use the buttons at the far left of the Browser Bar.

Browser Bar
Browser Bar

Besides showing the number of displayed and selected images, the Browser Bar also allows for quick filtering of the displayed images by Image Type. The same can be accomplished by choosing one of the View ▸ Image Type menu items. A version’s image type can be edited in the Version Inspector. Although it may contain any value, Observatory gives special meaning to the following values:

Standard image types
Image type Description
MasterBias A master bias frame.
MasterDark A master dark frame.
MasterFlat A master flat frame.
Bias A bias frame.
Dark A dark frame.
Flat A flat frame.
Light A regular image.

If, for example, you click the Dark button in the Browser Bar, the browser displays only those images that contain the value “Dark” in their image type. Hence, it will display dark frames, but also master dark frames. The Bias, Flat and Light buttons work similarly.

The Browser Bar also has a search field to quickly filter images by tag, name, filter name and status. Initially if you enter a search term it will filter by any of these attributes, but you can also explicitly select one in this search field.

To show or hide images that have been Matched, choose View ▸ Show/Hide Matched. To show or hide images you have rejected, choose View ▸ Show/Hide Rejected.

By default the browser is sorted by exposure date/time in descending order. This can be changed by choosing one of the View ▸ Sort By menu items. In the List Browser, you can also change the sorting by clicking the column titles. The selection is coupled to the above View ▸ Image Type selection. You can sort in ascending or descending order by

  • Name
  • Color Label
  • Rating
  • Status
  • Weight
  • Image Type
  • Exposure Date/Time
  • Exposure Duration
  • Filter Name
  • Center Right Ascension
  • Center Declination
  • Import Date/Time

The Image Browser

The Image Browser displays a thumbnail for each of the images in the currently selected collection in a vertical scrollable grid. It is shown by choosing View ▸ Browser ▸ Image (⌃⌘I). Below the thumbnail, the image’s name is displayed, and below that a subtitle. The contents of the subtitle is configurable using the View ▸ Subtitle menu items. The selection is coupled to the above View ▸ Image Type selection. For example, unless you change it, Observatory doesn’t display the Exposure Duration when the Bias Image Type Filter is enabled, but it does so for all other Image Type Filters. The subtitle may be any combination of

  • Rating
  • Status
  • Image Type
  • Exposure Date/Time
  • Exposure Duration
  • Binning
  • Canvas Size
  • Filter Name
  • CCD Temperature
  • Focal Length
  • Aperture Diameter

If you select a color label for an image, it is overlaid at the top-right corner on the thumbnail. It may also be overlaid with several badges:

Image Version Badges
Badge Description
MatchBrowserBadge The image version is astrometrically matched
FavoriteBrowserBadge It has been marked as a favorite
LockBrowserBadge It is locked
NoteBrowserBadge It contains a note
AttachmentBrowserBadge It has an attachment
LayerAdjustmentBrowserBadge It contains at least one layer adjustment
ManagedMasterBrowserBadge The master of the image version is a managed master
ModifiedMasterBrowserBadge Its master has been modified
MissingMasterBrowserBadge Its master is missing
ZeroWeightBrowserBadge It has been rejected (its weight is zero)
StackBrowserBadge It is a stack, comprising of multiple images
PickBrowserBadge It is the pick version of a stack
WeightBrowserBadge It is part of a stack and its weight has been adjusted

The size of the thumbnails in the Image Browser can be adjusted by moving the slider in the Browser Bar.

The List Browser

List Browser
List Browser

Use the View ▸ Columns menu items to choose which columns you want the List Browser to display. The selection is coupled to the above View ▸ Image Type selection. For example, unless you change it, Observatory doesn’t display the Exposure Duration column when the Bias Image Type Filter is enabled, but it does so for all other Image Type Filters. The following columns can be displayed in the List Browser:

  • Name
  • Badges
  • Color Labels
  • Rating
  • Status
  • Image Type
  • Exposure Duration
  • Binning
  • Canvas Size
  • Filter Name
  • Pixel Size
  • CCD Temperature
  • Constellation
  • Center Right Ascension
  • Center Declination
  • Center Azimuth
  • Center Altitude
  • Telescope
  • Focal Length
  • Aperture Diameter
  • Aperture Area
  • Camera
  • Guider
  • Observer
  • Observatory
  • Import Date/Time

The Date/Time column is required and cannot be hidden. The weight column is automatically shown if the focus is on a stack. Except for these two, you can reorder the columns by moving their headers, and many, but not all, you can also resize.

The Image Strip Browser

Show Browser & Editor
Show Browser & Editor

The image strip browser is similar to the image browser, but it displays the thumbnails in a horizontal scrollable strip. The thumbnails are of a fixed size. The image strip browser can only be displayed in combination with the Editor.

Image Strip Browser
Image Strip Browser

When the Browser and Editor are both shown, the Browser Bar contains buttons for all three browser types. They are all of fixed height. Note that the currently selected browser type in Browser & Editor view mode is independent from that of the Browser Only view mode, as is the image browser thumbnail size.

Browser & Editor Bar
Browser & Editor Bar

To quickly select an image, focus on its album and switch to Browser & Editor mode, double click it.

The Focus Bar

When you are working in an album, you will often want to collapse the sidebar (⌘0). To help you focus, the browser displays the Focus Bar if you have selected any collection in the sidebar. It displays the name and type of the currently selected folder, album, or smart album and allows you to traverse up the collection hierarchy using its Unfocus button (^⌘]).

Focus Bar
Focus Bar

If your album contains stacks, and you select one, the Focus Bar will show an additional button: Focus on Stack.

Focus Bar: Select Stack
Focus Bar: Select Stack

Click it, or press ^⌘[, and the browser will display the images the stack is made of. When focused on a stack, the Focus Bar displays three handy buttons to quickly select the stack’s pick image, all images comprising the stack, or the stacked image itself. With the Unfocus button (⌘]) you traverse up to the stack’s album.

Focus Bar: Focus on Stack
Focus Bar: Focus on Stack

To quickly focus on a stack, double click it.

Using the Editor

The Editor displays the currently focused image of the browser. It can be shown simultaneously with the browser by choosing Show Browser & Editor (⌥⌘⏎), or on its own by choosing Show Editor Only (⌘⏎). The latter is especially useful if you select all images you are working on beforehand in the browser.

Editor
Editor

It works in cooperation with the selections in the Histogram, Layers and Channels panels to display the image:

  • If the image contains multiple layers, then the Layers panel determines how they are composited together to form a single image, which shows up in the Editor’s canvas. The Layers panel also is used to select the Active Layer. The information displayed in the Editor Bar is for the active layer only.

  • RGB images contain three channels. With the Channels panel you can change the visibility of any of them. In addition, and similar to the Layers panel, it can be used to select the Active Channels. If you select only one channel as being active, the information displayed in the Editor Bar is for that one channel only. For RGB images by default all channels are selected.

  • The Histogram panel not only displays the image’s histogram, but also allows you to quickly change the black and white points used for displaying the image in the editor. Even in its collapsed state you can quickly adjust the black and white points by selecting one of the percentile presets (Low, Medium, High and All) in its action menu.

Towards the top of the Editor, the name of the focused image is being displayed. If the image is a stack of images, the stack icon is shown left of the name. The center of the Editor contains the canvas. The current zoom (or magnification) level, as well as the option to change the zoom using the popup button can be found on the bottom right hand side of the Editor Bar. You can also choose View ▸ Zoom In (⌘+) and View ▸ Zoom Out (⌘-) to change the zoom. Choose View ▸ Actual Size (⌘1) to quickly zoom to 100%, and View ▸ Zoom to Fit (⌘9) to center and zoom the image to fit in the canvas.

If you have the Zoom in or out and Smart zoom gestures enabled in your trackpad system preferences, then you can also pinch with two fingers to zoom in and out, and quickly switch between the current zoom level and 200% by double-tapping the canvas with two fingers. You can also quickly zoom in and out by pressing the Option key while using a mouse’s scroll wheel.

The image can be moved around (panned) in the canvas using the scrollbars. Alternatively, you can click and drag the mouse pointer, or just use the panning gesture of your trackpad.

Editor Bar

Besides controlling the editor’s zoom level, the Editor Bar displays the current cursor pixel position as well as the pixel value at this position. For grayscale images only one value is displayed, but for RGB images up to three values may be displayed, one for each channel.

Editor Bar
Editor Bar

While you move the cursor over an image, you will occasionally see three concentric circles appear near the cursor position. You may need to switch to 100% or 200% to see it. It consists of an inner filled circle, the aperture, surrounded by a doughnut shape, the annulus. The sizes of these shapes are determined by the Centroid Settings.

Aperture and Annulus
Aperture and Annulus

The pixels in the annulus area around the cursor position are used to compute the local background value. This value is subtracted from the value for each pixel in the aperture area. The resulting values are then used to compute the centroid position. If successful, the FWHM of the gaussian profile is computed.

These values are displayed in the Editor Bar. For RGB images, the displayed values are an average over the selected channels, so its a good idea to select a single channel (e.g. Green).

If you select multiple image in the browser, only the focused image is displayed in the editor. You can use the Go Back and Go Forward buttons next to the zoom popup button to focus on another image in the selection, or press the ⌘[ and ⌘] keys. Here you can also blink between these images by pressing the Play/Pause Animation button.

Centroid Settings

At the far left of the Editor Bar is the Centroid Settings button. Clicking it reveals a popup window, which can be used to adjust the aperture radius, annulus gap and annulus width. The gap is a “dead zone” in which all pixels are ignored. It prevents stars near the target from being measured.

For best results, after you have located a few centroid positions in your image and measured their FWHM values, revise the aperture to the appropriate radius of 3–5 FWHM.

To close the popup window, click outside it or click the top-right button. With the button next to it you can reset the aperture radius, annulus gap and annulus width to their default values. With the first button you can hide the background, centroid and FWHM values from the editor.

The centroid settings are not only used for the editor, but also for the Photometry Inspector and when matching images.

Overlay Catalogs

Images that have been astrometrically matched (plate solved) contain all the information to relate image pixels to sky coordinates. These images are indicated in the browser with the Browser Badge for a Matched Image badge. If you move the cursor over an image that has been matched, the Cursor Inspector in the Measure tab along the right side of Observatory’s window will not only show its pixel position, but also the corresponding right ascension and declination.

In addition, the Editor canvas may overlay information of many astronomical objects onto your image. The Overlay menu allows you to toggle image scale, orientation and RA/dec grid, as well as the Messier and NGC/IC objects, galaxies from the PGC2003 catalog and stars of the Tycho–2 catalog. It optionally also overlays the positions of the solar system’s planets and Pluto onto your image. If you have the UCAC4 and/or USNO-A2.0 catalogs installed, these can be displayed as well.

Images that have not been matched can be matched by choosing Image ▸ Match… (⌃⌘M).

The Assistant Editor

Assistant Editor Toolbar Button
Assistant Editor Toolbar Button

By default, the editor only displays a single image canvas. This is called the The Standard Editor. Sometimes you may want to see multiple images at the same time, for example to

  • Compare two images;

  • Measure the FWHM of stars in a stacked image, and compare them with its source images;

  • Blink a set of images on one side, while manually inspecting individual images on the other side.

You can do this by choosing View ▸ Editor ▸ Assistant or by clicking the corresponding button in the toolbar. The canvas will split in two, with on the left hand side the standard editor, and on the right hand side the assistent editor. You can move the splitter horizontally.

Assistant Editor
Assistant Editor

Switch between them by clicking on their title bar. Alternatively choose View ▸ Editor ▸ Focus Next Editor (⌥⌘`) or View ▸ Editor ▸ Focus Previous Editor (⌥⇧⌘`). Use the + button to add an additional editor, or the - button to remove one. They are added above each other, separated by a splitter that can move vertically.

When you select images in the browser, the focused image is displayed in the active editor. Press the Option key while selecting an image in the browser to make it appear in the editor that is not currently selected.

To quickly switch back to a single Standard Editor, choose View ▸ Editor ▸ Standard or click the corresponding button in the toolbar.

Using the Virtual Observatory

Show Virtual Observatory
Show Virtual Observatory

With the Virtual Observatory you can search for and download images from 10+ professional astronomical image archives. Choose Show Virtual Observatory (⇧⌘F), or click the last of the four View buttons in the toolbar, and the center of the library window will be replaced by the Virtual Observatory, as are the inspectors.

Virtual Observatory
Virtual Observatory

Along the top you’ll find a row of buttons, one for each archive. Each of these buttons acts as a toggle, determining whether or not the selected archive will be searched. Below it is a text field where you enter the name, identifier or coordinates of the object you are interested in. By default Observatory will do an image search with a radius of 10 arcminutes, which is a little less than the angular diameter of the full moon. You can change this in the Search Radius field.

The supported archives are:

  • DSS

    The Digitized Sky Survey (DSS) is a digital version of several photographic atlases of the night sky, produced by scanning the plates using microdensitometers. Observatory supports both generations of DSS.

  • SDSS

    The Sloan Digital Sky Survey (SDSS) is a multi-filter imaging and spectroscopic redshift survey using a dedicated 2.5 m wide-angle optical telescope. Observatory provides access to the imaging catalog data of Data Release 12 (DR12), which is the final data release of SDSS-III.

  • PTF

    Palomar Transient Factory Archive (level 1). A survey using the Palomar Samuel Oschin 1.22 m Schmidt Telescope.

  • 2MASS

    The Two Micron All-Sky Survey (2MASS) is a survey of the whole sky in three infrared wavebands around 2 micrometers.

  • ESO

    The ESO Archive from the European Southern Observatory (ESO) includes images obtained with the VLT (8.2 m), VST (2.6 m), VISTA (4.1 m), NTT (3.6 m) and the ESO 3.6 m telescopes. To download these images, you’ll first need to enter your ESO user portal account name and password in the Preferences. Creating it is free, and can be done at http://www.eso.org/userportal/. On that page, select I would like to create a new account, and follow the instructions.

  • GOA

    Gemini Observatory Archive. The Gemini Observatory consists of two 8.19 m telescopes, the Gemini North in Hawaii and the Gemini South in Chile.

  • KOA

    The W. M. Keck Observatory is a two-telescope astronomical observatory near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes feature 10 m primary mirrors. Through the Keck Observatory Archive (KOA), Observatory provides access to the images obtained with the NIRC2 instrument.

  • HST

    The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990, and remains in operation. This button gives access to the HST Mikulski Archive for Space Telescopes.

  • HLA

    The Hubble Legacy Archive of the Hubble Space Telescope.

  • WISE

    Wide-field Infrared Survey Explorer (WISE AllWISE Atlas). WISE is a 0.4 m NASA infrared-wavelength space telescope.

  • SHA

    Spitzer Heritage Archive (level 2). The Spitzer Space Telescope is a 0.85 m NASA infrared-wavelength space telescope.

To search for an object, enter its name, identifier or coordinates in the text box below the buttons. Observatory recognizes Messier, NGC/IC, Tycho–2 and PGC2003 identifiers, as well as hundreds of common names. Entries like “Whirlpool Galaxy”, “M 51”, “202.4696+47.1953” and “13 30+47 12” (without quotes) will all be resolved.

As soon as you enter anything, the resolved items with their celestial coordinates will be displayed immediately below the text field. For example, if you start entering “Whirlpool Galaxy”, without quotes, Observatory will display

Typing “Whirlpool Galaxy”
Typing “Whirlpool Galaxy”

after you have typed the “W”. The list will be further reduced as you type.

Typed “Whirlpool Galaxy”
Typed “Whirlpool Galaxy”

If the object you want to obtain images for is in the list, select it and click the Search button. Observatory will then search for all images in the selected archives, and display the results.

Although Observatory contains data for millions of objects, you may find that it cannot always resolve the object you are looking for. For this reason, the SIMBAD and NED web services are integrated with the Virtual Observatory. After entering the target name or identifier, just click the corresponding buttons to have these services resolve your entry and add them to the list.

The results are initially sorted by exposure date, but you can change this by clicking one of the column headers. By clicking a second time, you change the sort order.

Your search may return thousands of results. One way to reduce the number of results is by deselecting the archives you are not interested in. You can reduce or extend search results this way even after you have performed the search. By reducing the search radius, the number of results will also be reduced.

Another way to reduce the number of search results is by filtering them using the Virtual Observatory Results Filter.

Virtual Observatory Results Filter
Virtual Observatory Results Filter

It allows you to reduce the number of results by target, instrument, filter name, description or identifier. You can specify which field you want to match, or you can have it match any of these fields by using “All”. For example, if you only want to include images obtained with the Hubble ACS instrument, you might enter “ACS” here.

Filter by HST ACS instrument
Filter by HST ACS instrument

If you select one or more results, the inspector on the right hand side will display more details of the selection. For many items preview images are available, which is indicated by a dot (). By expanding the Preview pane in the sidebar, you have quick access to these previews.

Items you have already in your library are gray in the results table. Sometimes you will also see items in red. This indicates that the data is still under the proprietary period.

To download images, select them and click the Import button. If you have selected the Add to album checkbox, they will be imported straight into the album that you have currently selected in the sidebar, if any, instead of the “Inbox”.

Whirlpool Galaxy
Whirlpool Galaxy

The images will be downloaded and imported in the background, and you can continue to search for other images or use Observatory in any way you wish. If you quit Observatory then any ongoing downloads will be cancelled though.

You can view the progress of downloads by clicking the Downloads button in the toolbar. In that popover, you can also cancel individual downloads, as well as clean up the list such that only downloads that are in progress are displayed.

The downloaded images are stored as Managed Master images in your library. If you wish to have access to them from outside Observatory, then you’ll need to export them by choosing File ▸ Export ▸ Managed Master…. This exports the original downloaded files.

If you press the key while selecting the Show Virtual Observatory menu item, it will change into Match Virtual Observatory (⌃⌥⌘F). If your currently selected image is Astrometric Matched, the Virtual Observatory will then use its center equatorial coordinates to initiate a search right away. This is handy way to search for images in the archives that cover the same area as your selected image.

Using the Inspectors

Along the right side of Observatory’s window are the Inspectors. Fully collapsible and consisting of the Image Version, Layer Adjustment, Measure, Stack and Album inspectors, as well as inspectors for attachments, channels, layers and the histogram, it provides access to most of the tools for adjusting selected images and their meta data.

The Image Version Inspector

When you choose one or more images in the Browser, the Image Version Inspector along the right side of Observatory’s window will display the metadata of the selection. This metadata is retrieved, normalized and stored in the Observatory library upon importing the images. You can edit this metadata here without altering your master images.

Version Inspectors
Version Inspectors

Towards the top, you’ll see a thumbnail of the image and its name. If you just imported the image, this may be the file name, but you can modify it here. Next to it is a lock icon. It allows you to lock the image version, to protect it against changes. If you marked your image as a favorite, or archived it, then you will see an indicator here too.

You can also modify the name directly in the Image Browser.

Unless the image version is locked, or its album is, you can edit most information presented in this inspector. You are not limited to editing the metadata for one image at a time. You can select many images, and the inspector will clearly indicate which metadata is common or different among them, and allows you to alter it for all selected images at once.

If you made an accidental change, just choose Edit ▸ Undo (⌘Z).

The inspector is organized in sections. You can collapse sections you are not interested in. You can also reorder the sections, by putting your mouse cursor between the disclosure triangle and section title, and clicking/dragging the section up or down to another position.

The Observation inspector

  • Type

    The image type. Although it may contain any value, Observatory gives special meaning to the values that are listed in the following table.

    Standard image types
    Image type Description
    MasterBias A master bias frame.
    MasterDark A master dark frame.
    MasterFlat A master flat frame.
    Bias A bias frame.
    Dark A dark frame.
    Flat A flat frame.
    Light A regular image.

    These values work in cooperation with the quick filter for image types in the Browser.

    Browser Bar
    Browser Bar

    For example, if you click the Dark button in the Browser Bar, the browser displays only those images that contain the value “Dark” in their image type. Hence, it will display dark frames, but also master dark frames. The Bias, Flat and Light buttons work similarly.

    Observatory automatically initializes the image type attribute when importing FITS, XISF and SBIG images, but sometimes it may not be able to determine it, or you may have imported RAW images. Therefore, after importing images, it is recommended to check and correct the image types for the newly imported images. After the import, just click the Other button in the Browser Bar. The browser then displays those images that have image types other then listed above. Select all images for which you know they are of a certain type, and enter the correct value in the inspector. You do not need to select each image individually, since Observatory supports bulk editing.

  • Date/time

    The date and time the exposure was started (UTC). It is displayed in Year-Month-Day Hour:Minutes:Seconds format.

  • Duration

    The exposure duration in seconds. You may optionally include a unit when entering a value. For example, entering “10min”, “10m”, “600s” and “600” are equivalent. For calibration purposes it is important to have a correct value set for this attribute.

  • Binning

    Binning is the process of combining charge from adjacent pixels in a CCD during readout. It improves the signal-to-noise ratio, at the expense of reducing spatial resolution. If the image was acquired with binning enabled, this attribute contains the X and Y binning values. Otherwise these are set to 1.

  • Size

    The canvas size. Usually this is the same as that of the master image, but for stacks and adjusted images you may occasionally want to change it by choosing Image ▸ Resize Canvas. You cannot adjust the value in the inspector.

  • Filter

    The name of the filter that was used when the image was taken. For calibration purposes it is important to have a correct value set for this attribute, if any.

  • Pixel size

    The pixel size in micrometers. When binning is used, this is the effective pixel size (CCD pixel size × binning value).

  • CCD temperature

    The CCD temperature during the exposure in ℃. You may optionally include a unit when entering a value. For example, entering “253.15K”, “–4F”, “–20C” and “–20” are equivalent. For calibration purposes it is important to have a correct value set for this attribute, if any.

  • Source

    The image source attribute is set by Observatory for images obtained using Virtual Observatory. You cannot adjust the value in the inspector. Possible values are:

    • Digitized Sky Survey
    • Sloan Digital Sky Survey
    • ESO Archive
    • Hubble Data Archive
    • Hubble Legacy Archive
    • Two Micron All Sky Survey
    • Keck Observatory Archive
    • Wide-field Infrared Survey Explorer Archive
    • Spitzer Heritage Archive
    • Palomar Transient Factory Archive
    • Gemini Observatory Archive
  • Identifier

    The image identifier. For manually imported images, this is the original file name. For images obtained using Virtual Observatory, this is a unique identifier for the image in the source archive. You cannot adjust the value in the inspector.

The Instrument inspector

  • Telescope

    The name or description of the telescope that was used for acquiring the image.

  • Focal length

    The effective focal length of the telescope or camera in millimeters. You may optionally include a unit when entering a value. For example, entering “2.5m”, “2500mm” and “2500” are equivalent.

  • Aperture diameter

    The effective aperture diameter of the telescope or camera in millimeters. You may optionally include a unit when entering a value.

  • Aperture area

    The effective aperture area of the telescope or camera in square millimeters. This is the area of the objective minus any obstruction.

  • Camera

    The name or description of the camera that was used for acquiring the image.

  • Guider

    A description of the guider or guiding method that was used while acquiring the image.

The Location inspector

  • Observer

    The name of the observer.

  • Observatory

    The name of the observatory.

  • Latitude

    The latitude of the observatory.

  • Longitude

    The longitude of the observatory.

The WCS inspector

The values in the WCS inspector cannot be changed directly. Instead, they are retrieved from the image when importing, or updated when plate solving was successful.

  • Constellation

    The constellation the center of the image falls in, as determined from the center right ascension and declination.

  • Center right ascension

    The right ascension of the center of the image.

  • Center declination

    The declination of the center of the image.

  • Pixel scale

    The pixel scale in arcseconds per pixel near the center of the image.

  • Position angle

    The position angle in degrees near the center of the image.

  • Center azimuth

    The azimuth of the center of the image at the time of the exposure.

  • Center altitude

    The altitude of the center of the image at the time of the exposure.

  • Air mass

    The air mass of the center of the image at the time of the exposure.

The Organize inspector

  • Label

    You can assign a color label to your image by clicking on one of these seven colored circles. The meaning of the different colors is up to you. For example, you could

    • Use different color labels for different locations.

    • Group images by telescope, aperture diameter or focal length by assigning color labels.

    • Assign a color label to images you have published online.

    • Use a color label to indicate the progress towards processing the image. For example:

      • red – Preprocessing phase;
      • orange – Linear post-processing phase;
      • yellow – Nonlinear post-processing phase;
      • green – Fully processed image.

      Please note that Observatory does not support all these phases of image processing itself.

    To remove the color label, click it for a second time.

  • Rating

    You can assign a 1–5 star rating to your image by clicking towards the right of this label. Drag the stars towards the left to remove the rating.

  • Status

    This attribute may contain an arbitrary textual or numeric value of your choice. The Browser Bar lets you filter images by this status attribute.

  • Tags

    Tags, or keywords, are a good way of organizing your images. You can add your own, but Observatory also adds them automatically when importing or when plate solving was successful. The Objects collection contains many predefined Smart Albums that use tags to quickly filter by object category.

The Note inspector

When you import an image that contains comments or a processing history, Observatory will copy them as a note associated with the image. But it also allows you to add your own notes to each of your images. With this inspector you can view and edit it. If you have selected it, you can even press ⌘F to search inside the note.

Albeit handy, there isn’t much room in the inspector. Choose Image ▸ Edit Note… (⌘') to open a much bigger, resizable Dialog for editing the note. There you can also press ⌘F to search inside the note, or click the icon near the bottom left of the Dialog.

The Layer Adjustments Inspector

Layer Adjustments are nondestructive image editing tools that adjust your image without permanently changing its pixels. You can edit and discard your adjustments or restore your original image at any time.

You can use them with regular image versions as well as with image versions that are part of a stack. As you will see later, some adjustment can only be used inside a stack.

To get started, select the image, and select the layer you wish to work with in the Layers Panel. Most of the time, your image only consist of a single layer, in which case you can skip this step.

Bring up the Layer Adjustments Inspector by either clicking the corresponding button along the right side of Observatory’s window, or by choosing View ▸ Inspectors ▸ Layer Adjustments.

When you first do this for an image, you’ll see that it has no adjustments. After all, when you have imported an image, its first image version is the same as the master image.

Layer Adjustments Inspector
Layer Adjustments Inspector

You add an adjustment by clicking the + button at the bottom right, and choosing one of the adjustments, or by choosing it in the Layer menu. This will add the adjustment to the Layer Adjustments Inspector. For example, if you choose Layer ▸ Rotate ▸ Rotate, it will add:

Layer Adjustment: Rotate
Layer Adjustment: Rotate

Here the rotation angle was changed to 20°. Most adjustments allow you to change some of their options.

You are not limited to adding layer adjustments to images individually. You can select multiple images and apply the same adjustments to each.

Adjustment basics

Adding adjustments

You add an adjustment by clicking the + button at the bottom right of the Layer Adjustments Inspector, and choosing one of the adjustments, or by choosing it in the Layer menu.

Removing adjustments

To remove any adjustment, click on the X button in the upper right hand corner of the adjustment.

Moving adjustments

Adjustment are applied in the order they are shown in the Adjustments Inspector. To move an adjustment up or down, just drag and drop it to the location you desire. Do this by putting your mouse cursor between the disclosure triangle and adjustment title, and dragging it up or down to another position.

Resetting adjustment values

You can reset all the values in an adjustment by clicking the circular arrow located between the visibility and delete buttons.

Adjustment: Reset
Adjustment: Reset

Visibility

Click on the eye button in the adjustment to toggle its visibility. The visibility determines whether it will participate as an adjustment. It is a handy way to see the effects of an adjustment on your image.

Adjustment: Visible
Adjustment: Visible

Adjusting parameters

Many adjustments have values you can adjust through popup buttons, sliders or number entry. Some adjustments contain options that can be manipulated directly on your image such as the rotation angle of the Rotate adjustment. To toggle the visibility of “on image” adjustment controls, click the HUD button (the circle with two dots). Click the HUD button again to hide it from the Editor canvas.

Adjustment: Show HUD
Adjustment: Show HUD

Resizing the image canvas

In Observatory, a layer consists of one (grayscale) or three (RGB) channels, which are all of the exact same size. An image consists of one or more of these layers. The image dimensions do not need to match those of its layers though, and the layers can be placed with different offsets in the image’s canvas. You can change the image dimensions by choosing Image ▸ Resize Canvas….

If you want the canvas to be large enough to encompass the largest layer in your image, choose Image ▸ Resize Canvas…, click Adjust canvas to fit layers and then the OK button. All layers will then be fully presented within the canvas boundaries.

Adjustments

Calibrate

Bias, dark and flat field correction using the calibration images from the Bias Calibration, Dark Calibration and Flat Calibration albums. The layer dimensions, CCD temperature (±0.5 ℃), exposure duration and filter name are taken into account for this. Archived calibration images are ignored.

The adjustment has the following options. Each is initialized from one of the calibration albums. You do not need to select a value for each option.

  • Master BIAS – Lists the bias frames that match the image’s dimensions and CCD temperature. Select one to apply, or None to not use bias calibration.
  • Master DARK – Lists the dark frames that match the image’s dimensions, CCD temperature and exposure duration. A matching exposure duration is not required if a Master BIAS is selected. Select one to apply, or None to not use dark calibration.
  • Master FLAT – Lists the flat frames that match the image’s dimensions, CCD temperature and filter. Select one to apply, or None to not use flat calibration.
  • Master DARK FLAT – Lists the dark frames that match the flat’s dimensions, CCD temperature and exposure duration. A matching exposure duration is not required if a Master BIAS is selected. Select one to apply, or None.

If you are not seeing the calibration images you had expected, make sure that the relevant metadata matches for your image and its calibration images.

Using an image for image calibration

Select the image, for example a master dark frame, and choose Image ▸ Move to Album ▸ Dark Calibration. Observatory will ask you for confirmation of modifying its image type when doing that.

If you created a master calibration image by stacking multiple images in Observatory, then you first need to create a snapshot of the stack’s current state by creating a Managed Master of it, since a stack cannot be used directly as calibration image. Select the stack and then choose Image ▸ New ▸ Master. Then choose Image ▸ Move to Album ▸ Dark Calibration to use it as a master dark.

Offset

Repositions the layer.

  • InterpolationNearest Neighbor or Bilinear.
  • Offset – X and Y offset.

Double Size

Doubles the size of the layer in both directions.

  • InterpolationNearest Neighbor or Bilinear.

Half Size

Reduces the size of the layer in both directions.

  • InterpolationNearest Neighbor or Bilinear.

Resize

Resizes the layer in both directions using a scaling factor.

  • InterpolationNearest Neighbor or Bilinear.
  • Scale – The scaling factor.

Binning

Reduces the size of the layer in both directions by binning the pixels.

  • Binning – The X and Y binning values.

Pixel Aspect Ratio

Adjusts the pixel aspect ratio.

  • InterpolationNearest Neighbor or Bilinear.
  • Pixel Aspect Ratio

Crop

Crops the layer to the given bounds.

  • Bounds

Mirror

Reverses the layer’s left and right.

Flip

Flips the layer upside down.

Rotate Left

Rotates the layer 90° counterclockwise.

Rotate Right

Rotates the layer 90° clockwise.

Rotate

Rotates the layer at an arbitrary angle.

  • InterpolationNearest Neighbor or Bilinear.
  • Angle – Angle in degrees.

Normalize

Adjusts the pixel values of a layer such that its background or overall brightness matches that of the stack’s pick.

This adjustment can only be applied to images which take part of a stack.

  • NormalizeBackground or Linear. If Background is chosen, then for each of the layer’s channels the pixel values are adjusted such that the channel’s median is equal to that of the corresponding pick’s channel. If Linear is chosen, the pixels are furthermore adjusted such that the standard deviations match as well.

Avoid using this adjustment when creating master bias or dark frames. Instead, if you have outliers in bias or dark stacks, remove those images from the stack or reject them by choosing Stack ▸ Reject.

Align

Aligns the layer with the stack’s pick. For RGB images the green channel is used for the image registration.

This adjustment can only be applied to images which take part of a stack.

  • InterpolationNearest Neighbor or Bilinear.
  • TypeLinear, Quadratic or Cubic. Typically you would choose the Linear transformation, but if your images are optically distorted Quadratic may lead to better results.

Arithmetic

Add a value to every pixel of the layer, subtract a value from every pixel of the layer, multiply a value with every pixel of the layer or divide every pixel with a value. Invalid (hot, missing) pixels are ignored.

  • OperationAdd, Subtract, Multiply or Divide.
  • Term

The Measure Inspector

When you focus on an image in the Editor, the Measure Inspector along the right side of Observatory’s window allows you to obtain more information from the image pixels themselves.

Measure Inspectors
Measure Inspectors

The inspector is organized in sections. You can collapse sections you are not interested in. You can also reorder the sections, by putting your mouse cursor between the disclosure triangle and section title, and clicking/dragging the section up or down to another position.

The Match… button towards the bottom of the inspector is equivalent to choosing Image ▸ Match… (⌃⌘M). Click it to plate solve the image. If the image already has been plate solved, the Unmatch button is displayed instead, which is equivalent to Image ▸ Unmatch. It is recommended to plate solve your non-calibration images, because it enables many features of Observatory (overlays, automatic tagging, etc).

The Cursor inspector

When you move the cursor over the image, this inspector will display the cursor’s position and the pixel value. In addition, if your image has been plate solved, it displays the right ascension and declination at the cursor position.

The Image Statistics inspector

This inspector displays the minimum, maximum, mean and median pixel values of the image. The number of pixels that were used for this may be less than the total number of pixels in the image, because Observatory skips invalid or missing pixels for these computations.

For an RGB image, the inspector displays the range of these values over the red, green and blue channels. To see the values for one channel only, select it in the Channels panel.

If you click the Reset button (the curly arrow) in this inspector, the inspector will toggle between a centered 100×100 pixel selection, and the complete image. Use this to compare the overall statistics with that of the center of the image.

Click the HUD button (the circle with two dots) in the inspector to make the selection rectangle visible in the Editor. You can click and drag it around, resize it from each end and corner. The mouse cursor changes its shape depending on the cursor position. The image statistics are refreshed each time you pause the dragging. You don’t need to release the mouse button, just pause the dragging itself.

Click the HUD button again to hide the selection from the Editor canvas.

The Photometry inspector

This inspector allows you to perform basic aperture photometry and Gaussian PSF fitting on your image.

For an RGB image, the first thing you should do is select the channel for which you want this to be measured. If you don’t, then the displayed values will be an average of the red, green and blue channels. Select the channel in the Channels panel.

Then, you should adjust the centroid settings in the Editor Bar such that the aperture is at least 3 times the FWHM as displayed in the Editor Bar for the to be measured stars. Also adjust the gap and annulus such that it contains mostly background pixels. You may deviate slightly from this to ensure that there are not multiple stars inside the aperture.

Now click the HUD button in the inspector. You will see two circular markers appear at the center of your image, initially on top of each other. You can drag these around and place them on the stars you want to measure (they “snap” in place when they detect a star). One is labeled V, and the other is labeled C. Far easier than dragging them, is just clicking on a star, which places V, and Option-clicking on the comparison star, which places C.

You will see that Observatory fills in many values in the Photometry Inspector when you do. If you know the magnitude of C, fill it in, and Observatory computes that of V.

If the image has been plate solved, the Photometry Inspector will automatically attempt to provide the magnitude of the selected comparison star from the Tycho–2, UCAC4 or USNO-A2.0 catalogs.

Displayed in the inspector are:

  • V – The selected position of the to be measured star, V.
  • C – The selected position of the comparison star, C.
  • Centroid – The computed centroid position of V.
  • Gaussian – The computed center position of the best fitting gaussian profile for V.
  • FWHM – The minimum and maximum FWHM of the two-dimensional gaussian profile of V.
  • Flattening – The ellipticity of the gaussian profile. Usually it is not completely round (0), because of seeing and tracking issues.
  • FWHM angle – The planar angle of the elliptical gaussian profile.
  • Gaussian peak – The peak of the best fitting gaussian profile.
  • Background – The annulus background value and sigma.
  • Flux – The sum of valid aperture pixel values minus the background of V.
  • C flux – The sum of valid aperture pixel values minus the background of C.
  • C mag – The known magnitude of C, for the chosen wavelength.
  • Mag – Computed magnitude of V.

Click the HUD button again to hide the markers.

Photometry Inspector
Photometry Inspector

The Astrometry inspector

Use this inspector if you wish to measure positions of stars in your image, their mutual distance and position angle. Although not required, it is best to plate solve the image, because only then will Observatory be able to compute it all.

For an RGB image, the inspector uses the average centroid positions over the red, green and blue channels. To obtain the results for a single channel only, select it in the Channels panel.

As with the Photometry inspector, make sure to adjust the centroid settings in the Editor Bar to obtain the best results.

Click the HUD button, and position or move the circular markers as described above. Click on a star to place A, and Option-click on a star to place B.

The inspector displays:

  • A – The selected position of star A.
  • B – The selected position of star B.
  • RA – The right ascension of A and B.
  • Dec – The declination of A and B.
  • Separation – The separation in pixels of A and B.
  • Planar angle – The angle between A and B in degrees.
  • Angular separation – The angular separation in degrees, arc minutes and arc seconds of A and B.
  • Position angle – The position angle in degrees.
Astrometry Inspector
Astrometry Inspector

The Stack Inspector

When importing images, it is best to organize them in albums. Not only to keep things organized, but also because only images that are filed in albums (hence not in Inbox) can be stacked. Image stacking is a digital image processing technique which combines multiple images into one to obtain a single high quality image.

For example, you may want to combine a set of dark frames into a single master dark. Or you may want to calibrate, align and combine images into a single one.

If you have a set of images in an album that you wish to stack, select them, and then choose Stack ▸ Stack. This will create a single stacked image from all those source images. Usually the images you want to stack will be of the same type, dimensions, have the same exposure duration, are taken at nearly equal CCD temperatures, etc. Observatory therefore also has an alternative method of stacking: by selecting all images in an album, and then choosing Stack ▸ Auto-Stack, observatory will create multiple stacks, taking the image type, dimensions, etc into account.

When you stack images in the browser, they are replaced by a single image. You can recognize these from their stack badge:

Stack Browser Badge
Stack Browser Badge

What happened is that Observatory created a new image by averaging the corresponding pixels of your original images. If you switch to the Stack Inspector along the right side of Observatory’s window, you’ll see that the stack type is “Average”.

Stack Inspector
Stack Inspector

You can choose between the following stack types:

  • Layer

    Each source image is added as a separate layer of the target stack image.

    If you select the stack image, and expand the Layers panel, you’ll see that it actually consists of multiple layers, not one, and each of these layers is named after one of the original images.

  • Sum

    Each corresponding pixel of every source image is added. Invalid or missing pixels are skipped.

  • Average

    The pixels of the source images are averaged. This is the default. Invalid or missing pixels are skipped.

  • Median

    The median of the source pixels is used for the target image. Invalid or missing pixels are skipped.

  • Sigma Clip

    Similar to Average, but rejecting outlier values.

    First the mean and the standard deviation of corresponding input pixels are computed. Then the value that is farthest from the mean is selected. If the difference between this value and the mean is less than or equal to the value of the threshold parameter times the standard deviation from the mean, then the mean is returned. If on the other hand the difference is greater, then this outer value is discarded from the set of input values and the mean of this new input range is returned.

When you select a stack, and choose Image ▸ Focus on Stack (^⌘[), or click the Focus on Stack button in the Browser Focus Bar, the Browser will display the images that you used to create the stack. If you switch to the Browser List View, you’ll see a property that is unique to images that are part of a stack: Weight.

Focus Bar: Focus on Stack
Focus Bar: Focus on Stack

Initially the weight for all images comprising a stack is 100%. This means they take fully part in the creation of the stack image. Sometimes however you may want to give a higher priority to the sharpest images in the stack, and use less sharper images to reduce noise. All the above listed stack types take the weight into account when computing the stack image.

To adjust the weight, select all images comprising the stack (click the button), and choose one of the options under Stack ▸ Auto-Weight. Observatory will then compute a weight for each of the images. The choices are:

  • Background

    Computes the background value of each image. Assigns the highest weight to the images with the lowest background value.

  • FWHM

    Computes the average FWHM value for the stars in each image. Assigns the highest weight to the images with the smallest FWHM. In other words, the sharpest images receive the highest weight.

  • FWHM (brightest)

    Computes the FWHM value of the brightest star in each image. Assigns the highest weight to the images with the smallest FWHM.

  • Star Peak

    Computes the peak of the best fitting Gaussian profile for each star in each image. Assigns the highest weight to the images with the highest average peak.

  • Star Peak (brightest)

    Computes the peak of the best fitting Gaussian profile of the brightest star in each image. Assigns the highest weight to those images with the highest peak.

For RGB images, it is important to select the channel for which you want this to be measured. If you don’t, then the values will be an average of the red, green and blue channels. Select the channel in the Channels panel.

You can also reject an image altogether, by choosing Stack ▸ Reject (⌃⌘0), increase or decrease a weight by choosing Stack ▸ Promote (⌃⌘=) or Stack ▸ Demote (⌃⌘-), and reset it to 100 % by choosing Stack ▸ Accept (⌃⌘1).

While combining images, Observatory will also use each source image’s layer opacity as a weight.

You can add layer adjustments to the images comprising a stack. For example, you can calibrate each, double them in size, and then align them with each other. The stack image is automatically updated whenever you make changes to the stack. Most of these layer adjustments are also available to images that are not part of a stack, but some (e.g. align) are only available for images in a stack because they require a reference image. This reference image is call a Pick. When creating a stack, initially the Pick is the image with the earliest exposure time, but you can change it by choosing Stack ▸ Pick (⌃⌘8).

Because the stack image is managed by Observatory (it is automatically generated and updated), you cannot manipulate that image directly. To do that, you’ll need to select it and choose Image ▸ New ▸ Master. This will freeze the current state of your stack image into a new managed master. You would do this also when you create a master calibration frame through stacking, by creating and then moving that managed master to one of the calibration albums.

Note that although you can create a single stack for a set of images, because creating versions is light-weight (choose Image ▸ New ▸ Duplicate Version), for experimentation with the weights it may be useful to create multiple stacks for the same master images.

We regularly add videos to our website that demonstrate certain aspects of Observatory, including calibration and stacking. Choose Help ▸ Videos to see them.

The Album Inspector

When you choose a folder, album or smart album in the Library Navigator of the Sidebar, the Album Inspector along the right side of Observatory’s window will display the metadata of the selected collection.

Album Inspectors
Album Inspectors

Towards the top, you’ll see an icon to help you quickly identify the type of selected collection. Next to it is its editable name and a lock icon. It allows you to lock the collection, to protect it and its contents against changes. If you marked the collection as a favorite, or archived it, then you will see an indicator here too.

Unless the collection is locked, you can edit all information presented in this inspector. If you made an accidental change, just choose Edit ▸ Undo (⌘Z).

The inspector is organized in sections. You can collapse sections you are not interested in. You can also reorder the sections, by putting your mouse cursor between the disclosure triangle and section title, and clicking/dragging the section up or down to another position.

The Organize inspector

  • Label

    You can assign a color label to your collection by clicking on one of these seven colored circles. The meaning of the different colors is up to you. For example, you could

    • Assign a color label to albums you have published online.

    • Use a color label for albums to indicate the progress towards processing the images contained within. For example:

      • red – Preprocessing phase;
      • orange – Linear post-processing phase;
      • yellow – Nonlinear post-processing phase;
      • green – Fully processed images;
      • blue – Currently acquiring images in this album.

      Please note that Observatory does not support all these phases of image processing itself.

    To remove the color label, click it for a second time.

  • Rating

    You can assign a 1–5 star rating to your album by clicking towards the right of this label. Drag the stars towards the left to remove the rating.

  • Status

    This attribute may contain an arbitrary textual or numeric value of your choice. The search field in the Library Navigator lets you filter collections by this status attribute.

  • Tags

    Tags, or keywords, are a good way to organize your collections. The search field in the Library Navigator lets you filter collections by tags.

The Note inspector

You can add notes to each of your collections. With this inspector you can view and edit it. If you have selected it, you can even press ⌘F to search inside the note.

Albeit handy, there isn’t much room in the inspector. Choose Album ▸ Edit Note… (⌥⌘') to open a much bigger, resizable Dialog for editing the note. There you can also press ⌘F to search inside the note, or click the icon near the bottom left of the Dialog.

The Attachments Panel

During an observation session you often take notes in a text document, or you might have collected research papers for some of the objects in an image or album. With Observatory you can attach these files to images and collections, so you can quickly look into or open them while working in Observatory.

To attach a file to an album, select the album and choose Album ▸ Attach File…. You are presented with a Dialog where you can select the file or files to attach. Usually you would link the attachments, but you can also decide to embed them in the library by selecting Embed the file in the library instead of the default Create a link to the file. Click the Select button to attach the file or files.

Note that when embedding attachments, Observatory will make sure that if you attach the same file to multiple collections or image versions, it will only embed it once.

The attachments appear in the Attachments Panel along the right edge of Observatory’s window. It has a disclosure button at its left which, when clicked, reveals and hides the panel. The click area actually covers the whole panel’s title bar, so you don’t have to be too accurate when clicking. Alternatively you can choose View ▸ Inspectors ▸ Show/Hide Attachments.

Collection Attachment
Collection Attachment

You can attach files to folders, albums and smart albums. These kinds of attachments are indicated in the panel with the appropriate icon for the collection type. If you see a curly arrow next to it, you know it is a linked attachment, and not an embedded one.

Similarly you can attach files to individual image versions. Select the images in the Browser and choose Image ▸ Attach File…. If you have the album selected at the same time, you still have the choice to attach it to the album instead of the individual images.

Image Attachment
Image Attachment

An alternative to using the main menu for attaching files is clicking the + button in the Attachments panel. Here you can also remove attachments, by selecting them and clicking the - button.

The Attachments panel displays a thumbnail of the attachment, and you can look at it up-close by selecting the attachment and clicking the eye-button. This will open a standard Quick Look window.

More options can be found in the action menu of the panel, as well as the contextual menu:

  • Open

    Open the attachment with its default application.

  • Open With

    Open the attachment with one of the listed applications.

  • Quick Look Attachment

    The same as clicking the eye-button.

  • Show in Finder

    Opens a Finder window with the attachment file selected.

The Import Dialog contains an Attach other files option, which is enabled by default, that will have Observatory attach (link) any file that is not an image to the generated collections.

The Channels Panel

Near the bottom of the Inspectors along the right edge of Observatory’s window, is the Channels panel. It has a disclosure button at its left which, when clicked, reveals and hides the panel. The click area actually covers the whole panel’s title bar, so you don’t have to be too accurate when clicking. Alternatively you can choose View ▸ Inspectors ▸ Show/Hide Channels.

Channels
Channels

Channels are grayscale images. They are created automatically when you open an image. The image’s color mode determines the number of color channels created. For example, an RGB image has a channel for each color (red, green, and blue), while a grayscale image has only a single channel.

The Channels panel lists all channels in the image. A thumbnail of the channel’s contents appears to the left of the channel name. It is automatically updated as you edit the channel.

Show or hide channels

You can use the Channels panel to view any combination of channels in the Editor. Click in the eye icon next to the channel to show or hide that channel. Observatory requires you to have at least one visible channel, so you are not able to hide the channel of a grayscale image.

Select channels

You can select one or more channels in the Channels panel. The names of all selected, or active, channels are highlighted in the panel. Many operations in Observatory are applied to the active channels of the active layer only. For example, by default all channels are selected for RGB images, and the Editor Bar will display the pixel value at the cursor position for each channel, and the centroid position will be an average over the three channels. By selecting only the green channel in the Channels panel, making it the active channel, the Editor Bar displays only the green pixel value, and the computed centroid position is that of the green channel only.

Because it is otherwise easily overlooked, the background color of the histogram in the Histogram panel is a handy indicator of the currently selected active channels.

The Layers Panel

Near the bottom of the Inspectors along the right edge of Observatory’s window, is the Layers panel. It has a disclosure button at its left which, when clicked, reveals and hides the panel. The click area actually covers the whole panel’s title bar, so you don’t have to be too accurate when clicking. Alternatively you can choose View ▸ Inspectors ▸ Show/Hide Layers.

Layers
Layers

Layers are like sheets of stacked tracing paper. You can see through transparent areas of a layer to the layers below. You move a layer to position the content on the layer, like sliding a sheet of tracing paper in a stack. You can also change the opacity of a layer to make content partially transparent.

Layers are composited together to form a single image which shows up in the Editor.

The Layers panel in Observatory lists all layers in an image. You can use the Layers panel to show and hide layers, select and rename them, and lock or unlock them. You can access additional commands and options in the Layers menu as well as the Layers panel action menu.

The Layers panel also is used to select the Active Layer. Information in the Editor Bar, the Measure Inspector, the Layer Adjustments, and many other operations in Observatory always act on the Active Layer.

The Histogram Panel

Near the bottom of the Inspectors along the right edge of Observatory’s window, is the Histogram panel. It has a disclosure button at its left which, when clicked, reveals and hides the panel. The click area actually covers the whole panel’s title bar, so you don’t have to be too accurate when clicking. Alternatively you can choose View ▸ Inspectors ▸ Show/Hide Histogram.

Histogram
Histogram

The histogram is a graph which shows how many pixels are in the image in different brightness ranges. The darkest pixel represented is at the left side, and the brightest pixel is at the right side. The highest point on the graph corresponds to the most common brightness level in the image. The vertical scale usually is logarithmic, but it can be changed to linear using the histogram action menu.

The histogram allows you to conveniently adjust the brightness and contrast of the displayed image without affecting the contents of the image. The red caret controls the black level. Moving it leftwards makes the background of the image lighter. The green caret controls the white level. Moving it leftward increases the image contrast, but also tends to saturate bright parts of the image. The contrast is highest when the two carets are close together.

The carets are affected by the two fields near the bottom of the panel. They can also be dragged with the mouse. In addition they can be moved left or right in steps by clicking in the area left or right of them.

Histogram Action Menu
Histogram Action Menu

Instead of manually adjusting the black and white points, you can also use one of the percentile presets in the histogram action menu. Even in its collapsed state you can quickly adjust the black and white points this way. The available settings are:

  • Low – low contrast setting with a dark background.

  • Medium – medium contrast setting with a dark background.

  • High – high contrast setting with a dark background.

  • All – adjust so that the brightest pixel is set to the maximum brightness, and the zero level is set to black.

RGB Histogram
RGB Histogram

For RGB images, the histogram panel displays the histogram for each selected (active) channel. By default all the channels are selected, but you can select one channel, for example Green, using the Channels panel. The background color of the histogram is a handy indicator of which channels are active for a given image.

RGB Histogram – Green Channel Only
RGB Histogram – Green Channel Only

Plate Solving

If you import images or download them through Virtual Observatory, those that have been plate solved, .i.e., contain all information to relate image pixels to sky coordinates, will be shown with a special badge in the browser:

Matched Image Browser Badge
Matched Image Browser Badge

Observatory refers to these images as having been matched. The reason for using this slightly different term is that Observatory performs extra steps for these images:

  • It automatically generates tags so you can more easily find the images.

    For example, if you import a plate solved image of M 1, Observatory will automatically tag it with m1, the equivalent ngc1952, the snr tag to indicate that this is a supernova remnant, as well as additional tags for other objects in the image.

    You can search for images containing these tags in the Browser by typing them in its search field, as well as by creating Smart Albums in the Sidebar or by using one of the predefined ones. In this case, if you select the predefined Smart Album Objects ▸ Nebulae ▸ Supernova Remnants in the Sidebar, your M 1 image will appear in the Browser.

  • It computes additional information, for example the constellation the center of the image falls in.

Other benefits of matched images in Observatory are:

  • The editor displays overlays: image scale, orientation, RA/Dec grid, but also various built-in and external catalogs.

  • The Astrometry Inspector displays right ascension and declination coordinates, angular separation of stars and their position angle.

  • The Photometry Inspector will automatically attempt to provide the magnitude of the selected comparison star from the Tycho–2, UCAC4 or USNO-A2.0 catalogs.

If one or more of your images are not plate solved, you can ask Observatory to do this for you. Select one or more images, and choose Image ▸ Match… (⌃⌘M).

Astrometric Match
Astrometric Match

If Observatory can find coordinates in the image metadata, it will shown them in the Dialog that appears. Images often contain valid coordinates, but not all image orientation and scale information, and this may suffice for Observatory to fully plate solve the image. Do this by clicking the Match All button.

If you started with multiple images, multiple coordinates may be returned. If they all contained coordinates, you once again click Match All, but if only a few contained coordinates, or you want the plate solver to use only one of those retrieved coordinates, select it and click the Match button.

Object Lookup

Your image may not contain any coordinates of course. The master FITS or XISF file may not contain this information, or you are using a different file format (e.g. SBIG or RAW). In such case, or when the coordinates are incorrect, you need to provide a hint to Observatory.

Astrometric Match: Lookup Object
Astrometric Match: Lookup Object

Just type the name of the object in the image, its catalog identifier or its coordinates in the text field towards the top of the Dialog. Observatory will attempt to resolve your entry, and display the coordinates and description. Observatory is able to resolve many common names used for objects, as well as Messier, NGC/IC, PGC2003 and Tycho–2 objects. If it is unable resolve it, click the SIMBAD and NED buttons to have these services resolve it. For these two services an internet connection is required.

What about moving objects?

Currently, only “fixed” objects can be resolved, and their coordinates used as a starting point for the plate solver. If you for example enter “Neptune”, the table in the center of the Dialog will remain empty.

Observatory has one extra trick up its sleeve though. If the image version contains the name of a planet or Pluto in its name, and its exposure date/time is correct, choosing Image ▸ Match… will have Observatory compute the position of that object at that date/time, and display these coordinates in the Dialog.

This can be handy if you have for example an image of one of the fainter planets and their moons, like Uranus and Neptune, or even Pluto, with background stars, but you don’t know the coordinates of the image.

Currently this only works for the eight planets and Pluto of the solar system.

Detection & Matching Settings

If this was all there is to plate solving, then that would be great, but typically you will need to adjust the default settings to make it succeed.

Click on the triangle at the bottom left of the Dialog so you can make adjustments to the settings.

Astrometric Match: Detection and Matching Settings
Astrometric Match: Detection and Matching Settings

The following settings are available:

  • Detection sensitivity

    This slider determines the sensitivity of the star detector. If you move it all the way to the right, it detects stars that are only slightly above the background noise. If your image is noisy, you may want to increase it a notch, but if you make it too sensitive, it may detect false positives. The default usually is good for a well exposed image, but if you have a large image with many well exposed stars you may want to decrease the sensitivity, since it makes the star detector faster.

  • Use brightest N stars

    Limits the maximum number of extracted stars. The default is usually good, but you may want to increase it if you are uncertain of the pixel scale.

  • Frame size

    Determines the area of the image the star detector is using. When set to Automatic, the detector uses the whole image except around the corners, to ensure detected stars always completely fall within the image. Manual adjustments range from the center 25% of the image, to the center 50%, then 75% and the complete image. The automatic setting is recommended, but if you have a large image with optical distortions you may want to reduce the detection area.

  • Pixel scale

    The estimated pixel scale in arc seconds per pixel. It only needs to be an estimate, but if it is not accurate within a factor of two, this significantly reduces the chances on success. The reason is that the estimate is used in combination with the frame size above and the search radius below to retrieve the stars from the catalogs. This may lead to the situation that effectively for only a small area of the image stars are obtained from the catalogs, or for a way too large an area. If you don’t know the pixel size, you may want to try with a few different values, e.g. 1, 2, 3 or 0.5.

    If you check Use pixel scale from image then Observatory attempts to obtain the value from the image itself. If it cannot, then it will set it to 1x1, or 2x2 for 2x2 binned images, etc.

  • Reference catalog

    Observatory comes with the Tycho–2 catalog built-in. It is recommended to at least set it up with the UCAC4 catalog as well. Observatory will use the selected catalog for matching. The choices are Tycho–2, UCAC4 and USNO-A2.0. If set to Automatic, it will first try Tycho–2, then UCAC4 (if installed) and lastly USNO-A2.0 (if installed).

  • Search radius

    By default the frame size and pixel scale determine the area of the sky for which stars are retrieved from the catalogs for matching the brightest stars in the image. If your estimate for the pixel scale is inaccurate, or if your image is distorted and you only use the center of the image for the star detector, this may lead to the situation that too small an area of the catalogs is sampled for stars.

    Drag the search radius slider to the right to increase the area of the sky for which stars are retrieved from the catalogs.

  • Search spiral

    An alternative to adjusting the Search radius is to keep it to its default value, and let Observatory do a spiral search for matching. If you move the slider all the way to the left, no spiral search is performed. By default Observatory does a spiral search in an area that is approximately four times the size of the image. The area increases fast when you move the slider to the right, so use this with caution.

  • Maximum residual

    By default the maximum allowed RMS in arc seconds of the solution is the HWFM of the stars in the image. It is a reasonable default, but you can override this default here.

  • Minimum number of matches

    The minimum number of matches required for the solution usually depends on the catalog that was used for the match. When using the Tycho–2 catalog, Observatory requires less matching stars than for the UCAC4 catalog, which in turn requires less matching stars than the USNO-A2.0 catalog. You can override it here. The minimum is 3, but this may lead to false positives.

You can reset the settings to their default values by clicking the button towards the bottom right of Dialog. You can collapse the settings by clicking the triangle once again.

Please be aware that the star detector also uses the current centroid settings. You can change those by clicking the “target” button in the Editor Bar. Additionally, for RGB images, please note that currently the green channel is always used for matching, regardless the selection in the Channels panel.

Importing

The easiest way to create a new library is by dragging the folder containing your images from the Finder and dropping it on the Observatory application icon. You can save this library, or use this mechanism to quickly inspect the contents of a folder, and then discard the library afterwards. For example, you could create a temporary library to inspect the images of your most recent observation session this way.

To create a new empty library, click the New button in the welcome window, or choose File ▸ New Library.

Import images into a new library by clicking the Import Images… button in the center of the window. You can also choose File ▸ Import ▸ Images… (⇧⌘I) in the main menu, or in the action menu of the Source Folder Panel choose Import Images….

Import: Add source folders or images?
Import: Add source folders or images?

You may be asked to either import the whole folder of images, or add source folders first. Because of macOS imposed sandbox restrictions, Observatory needs to be given access to the folders containing the images. If you import a complete folder, then this is done automatically, but if you wish to import individual images from a folder, you need to provide Observatory access to the folder first. It is only relevant if you have not done so yet for the library. The folders you have given Observatory access to are referred to as Source Folders. You can see these folders by expanding the Source Folders Panel in the Sidebar.

If you choose to explicitly add Source Folders by clicking the Add Source Folders button in this Dialog, or by clicking the Add Source Folder… button in an empty library, or choosing File ▸ Import ▸ Add Source Folder… in the main menu or its equivalent in the action menu of the Source Folder Panel, you are presented with a Dialog where you can choose one or more folders. Towards the bottom of this Dialog click Add all subfolders as source folders if you wish to recursively add the subfolders as well. Click the Add Source Folder button finally to add them.

If you click the Import All Images button instead of Add Source Folders, you are presented with a Dialog where you can also initially only select folders, but in this case this serves as a means to add Source Folders as well as import the images contained within. You cannot select individual images, unless some of the folders have been added as Source Folders already. You are presented with the following options:

  • Add to album

    This option is only enabled if you have selected an album in the Sidebar before importing. If checked, the images will be imported into that album. If not checked, they will be added to the Inbox, or if you have the next option checked, they may be added to automatically generated albums.

  • When choosing folders, import all images of their subfolders

    If checked, the importing will be recursively traverse the folders.

  • Auto-Stack

    If checked, the images will be auto-stacked after importing.

  • Attach other files

    If checked, any file that is not an image will be attached (linked) to their corresponding generated folder and album.

After selecting the folders, click the Import button to add them as Source Folders, and import all their images.

If you did add Source Folders previously, importing images will lead to this same Dialog, but you will now have the added capability to import individual images.

Sharing, Printing & Exporting

Share

With Observatory you can quickly share one or more images with others. Just select them in the Browser and click the Share button in the Toolbar of the library.

Share
Share

Depending on your selections in the  ▸ System Preferences ▸ Extensions ▸ Share Menu settings, you will be presented with the ability to email the images, add them as a note to the Notes application, create a message in Messages, a Facebook post, a tweet on Twitter, etc.

Sharing an image by email
Sharing an image by email

Included in the message is the image, and usually also the image version name, basic metadata and the notes. What exactly is included depends on the service you are targeting. You can edit the information before sending it. The image is converted to JPEG with the current view settings.

Print

By selecting images in the Browser and choosing File ▸ Print… (⌘P) you can print images, their version name, basic metadata and the notes. Each selected version is printed on a separate page. If the image is matched, the image may be printed with the overlays.

Print
Print

Export as PDF

You can quickly create a PDF file from the images and some of their metadata you have selected in the Browser by choosing File ▸ Export as PDF…. It is a shortcut for printing to a PDF file. Each image, its version name, basic metadata and the notes is added to a separate page in the PDF. As is the case with printing, if the image is Matched, it optionally includes the overlays.

Export

Observatory has powerful image export capabilities that allow you to convert your images to different file formats, resizing them, apply file naming templates, all while storing them in folders that use naming templates.

You define these file format, file naming and folder naming template using the Export Preferences.

Export Format

The Export Format determines the output file format, as well its dimensions. These dimensions may be the same as those of the source image version, a percentage of its size, or resized to fit within a given rectangular size. You can define your own formats, or use one of the defaults:

Default Export Formats
Name Description
Original Size (FITS) Output as 32 bit floating point FITS file
Original Size (FITS 16) Output as signed 16 bit integer FITS file
Original Size (TIFF) Output as TIFF file
Original Size (JPEG) Output as JPEG file
Original Size (PNG) Output as PNG file
Large Size (JPEG) Output as JPEG file (fit within 1280 × 1280)
Large Size (PNG) Output as PNG file (fit within 1280 × 1280)
Medium Size (JPEG) Output as JPEG file (fit within 640 × 640)
Medium Size (PNG) Output as PNG file (fit within 640 × 640)
Small Size (JPEG) Output as JPEG file (fit within 320 × 320)
Small Size (PNG) Output as PNG file (fit within 320 × 320)

Folder Naming Templates

When you export images, you select an output folder where the images will be exported to. The images can be exported simply as files immediately in this output folder, or in a deeper subfolder structure which reflects certain aspects of each image or its album. The Folder Naming Template determines this subfolder structure.

Default Folder Naming Templates
Name Description
None Do not create subfolders
Observation Date Create YYYYMMDD subfolders, based on image exposure date
Album Create subfolders with lowercase name of image’s album
Name Create subfolders with lowercase image version’s name
Album / Observation Date Create nested subfolders based on album name and exposure date
Name / Observation Date Create nested subfolders based on version name and exposure date

File Naming Templates

When you export images, you can simply use the version name as output name, but also let various attributes of the image determine its file name. The File Naming Template defines this naming pattern.

Default File Naming Templates
Name Description
Master Bias Lowercase name for master bias
Master Dark Lowercase name for master dark
Master Flat Lowercase name for master flat
Processed Lowercase name for processed image
Name Lowercase version name

Exporting Images

To export images, select them in the Browser and choose File ▸ Export ▸ Image… (⇧⌘E). This will export the selected versions. If you wish to export their master versions instead, choose File ▸ Export ▸ Master Image…. In both cases you are presented with a Dialog where you select the export destination folder. In addition, the following options are shown:

  • Export Format

    The export format to be used for the export. This determines the file type and dimensions.

  • Folder Format

    The folder format to be used for the export. This determines the naming of the subfolders in the export destination folder, if any.

  • Folder Custom Name

    A custom name that may be referenced in the folder format template.

  • Name Format

    The file format to be used for the export. This determines the file naming.

  • Custom Name

    A custom name that may be referenced in the file format template.

After selecting the destination folder and the various options, click the Export button to start the export.

Exporting Managed Masters

If you have used Virtual Observatory to obtain images from professional observatories, these will be stored as Managed Masters in the library. They are indicated with a special badge in the browser:

Managed Master Browser Badge
Managed Master Browser Badge

To export these original, unmodified images, choose File ▸ Export ▸ Managed Master….

Note that the same badge is also used for Managed Masters that were created using Image ▸ New ▸ Master. These kinds of masters you can only export through one of the methods described in the section Exporting Images.

Plugins

Observatory contains plugins for FITS, XISF and SBIG images that automatically generate thumbnails for the Finder, allow you to preview them up-close in the Finder without opening any application, and will index their metadata for easy searching in the Finder. Observatory also comes with plugins for Acorn, so you can open these images at full bit depth directly in this powerful image editor for post-processing.

Quick Look

Quick Look lets you view a file’s contents by selecting it in the Finder and then pressing the spacebar. There’s no need to wait for the file to open in an application. Although macOS supports many types of images, the formats typically used for astronomy are not. Observatory therefore provides Quick Look generators for the following image formats:

  • FITS – Flexible Image Transport System (FITS) is a digital file format useful for storage, transmission and processing of scientific and other images. FITS is the most commonly used digital file format in astronomy. FITS images usually have a .fits, .fts or .fit extension.

  • XISF – Extensible Image Serialization Format (XISF) is a free file format for storage, management and interchange of digital images and associated data. XISF has been conceived and implemented as the native file format of PixInsight, an image processing software platform designed specifically for astronomical imaging, and developed by the company Pleiades Astrophoto S.L. These images usually have a .XISF extension.

  • SBIG – The SBIG format is the default format for saving images when using the SBIG CCDOPS image acquisition software. These images usually have a .ST7, .ST8, .ST9 or .SBIG extension.

To zoom in on an image when the Quick Look window is open, hold down the Option key. If you have PixInsight installed then there’s an Open with PixInsight button towards the top of the window, which when clicked will open the image in PixInsight.

Finder: Quick Look
Finder: Quick Look

As can be seen in the above screenshot, the plugins also generate image thumbnails for the Finder windows. In addition they are used in its Cover Flow view and for the Finder’s Get Info window. They even appear in the Dialog for opening files (instead of generic icons), in any application. In these Dialogs you can also view a file’s contents up-close by pressing spacebar.

PixInsight & Observatory: Open File & Quick Look
PixInsight & Observatory: Open File & Quick Look

Spotlight

Spotlight is a powerful macOS search technology that makes searching for files easy. Using Spotlight, you can search for things using attributes such as the width and height of an image in pixels, or its exposure time. Information like this (called metadata) is embedded in a file by the application that created it. Spotlight’s power comes from being able to extract, store, update, and organize the metadata of files to allow fast, comprehensive searches.

Spotlight uses Quick Look technology to display thumbnails and full-size previews of the documents returned in a search. As is the case with Quick Look, although macOS supports many types of images, the formats typically used for astronomy are not. Observatory therefore also provides Spotlight importers for the following image formats:

  • FITS – Flexible Image Transport System (FITS) is a digital file format useful for storage, transmission and processing of scientific and other images. FITS is the most commonly used digital file format in astronomy. FITS images usually have a .fits, .fts or .fit extension.

  • XISF – Extensible Image Serialization Format (XISF) is a free file format for storage, management and interchange of digital images and associated data. XISF has been conceived and implemented as the native file format of PixInsight, an image processing software platform designed specifically for astronomical imaging, and developed by the company Pleiades Astrophoto S.L. These images usually have a .XISF extension.

  • SBIG – The SBIG format is the default format for saving images when using the SBIG CCDOPS image acquisition software. These images usually have a .ST7, .ST8, .ST9 or .SBIG extension.

These Spotlight importers ensure that you can search for astronomical images using the following attributes in the Finder:

  • Title – The object name or target name, e.g. OBJECT FITS keyword.

  • Device model – A combination of the telescope, instrument and detector used for the observation, separated by semi-colons, e.g. TELESCOP, INSTRUME and DETECTOR FITS keywords.

  • Location – The name of the location where the image was obtained, e.g. ORIGIN FITS keyword.

  • Authors – The names of the observers, e.g. OBSERVER FITS keyword.

  • Kind – The file type, e.g. Flexible Image Transport System.

  • Identifier – The archive or root file identifier, e.g. ARCFILE FITS keyword.

  • Filter name – The filter used for the observation, e.g. FILTER FITS keyword.

  • Image type – The image type, e.g. IMAGETYP FITS keyword.

  • Detector temperature – Detector temperature in ℃, e.g. CCD-TEMP FITS keyword.

  • Right ascension – The center right ascension of the image, e.g. RA FITS keyword.

  • Declination – The center declination of the image, e.g. DEC FITS keyword.

  • Equinox – Equinox, e.g. EQUINOX FITS keyword.

  • Epoch – Epoch, e.g. EPOCH FITS keyword.

  • Content created – Exposure date & time, e.g. DATE-OBS and TIME-OBS FITS keywords.

  • Dimensions – Only for display purposes, the image width and height in pixels.

  • Axis – The number of axis of the image file. Only indexed if not exactly 2.

  • Pixel width – The width in pixels.

  • Pixel height – The height in pixels.

  • Pixel count – The total number of pixels in the image (width * height).

  • Exposure time – The exposure duration in seconds, e.g. EXPTIME FITS keyword.

  • Bits per sample – The number of bits per sample, e.g. BITPIX FITS keyword.

  • Focal length – Focal length in mm, e.g. FOCALLEN FITS keyword.

The attribute names were chosen to match those of image formats natively supported by macOS, when applicable, so there’s no need need for separate searches for, say, DNG files and FITS files.

Some of this extracted metadata is displayed in the More Info section of the Finder’s Get Info window, which is displayed if you select an image and choose File ▸ Get Info (⌘I). The preview is generated by the Quick Look generator.

Finder: Get Info
Finder: Get Info

To invoke Spotlight, you would usually press ⌘spacebar or click the magnifying glass icon at the right of your menubar. Much more advanced searches can be performed by searching in the Finder. Open a Finder window and click in the search field at the top, or press ⌘F to open a new search window or convert an open Finder window into a search window.

If the Finder displays your search results in Icon view, you’ll probably want to switch to List view to get a better look at your results. You can then select the column headers to sort the results. If you want more column headers to be visible, press ⌘J and check other columns from the View Options window, or use the contextual menu of the column header (Control-click).

macOS Finder has an undocumented but very useful feature: If you move the folder containing your astronomical images into the Pictures folder, the contextual menu of the List view’s column header will also contain a Dimensions item. Select it, and a Dimensions column will be added to the folder’s Finder window. The information displayed is obtained from the Spotlight index, and because Observatory contains Spotlight importers for FITS, SBIG and XISF images, the Finder will now display the width and height in pixels for these files.

Another useful feature is that when you switch to Icon view and press ⌘J, by selecting Show item info in the View Options window, the image dimensions will be displayed below the image thumbnails.

The Finder window’s search bar contains several options for tailoring your results. When you start typing search terms, the Finder pops up a menu asking if you want to restrict your search terms to file names only. And you can click on This Mac to change the target of your search from the folder you were in when you started searching, to your entire Mac.

Finder: Search
Finder: Search

Adding criteria

To narrow down your results, start by selecting one of the criteria in the first menu. The default items in the menu are not very good choices for searching FITS, SBIG and XISF images, so click Other… here. Observatory’s Spotlight importer adds many attributes to the list. Click on the In Menu check box next to an item if you want it to appear in the search bar menus for easy access in the future.

Finder: Search Attributes
Finder: Search Attributes

Useful additions to the menu might be:

  • Device model – If your images were obtained with multiple telescopes or cameras.

  • Filter name – If your images were obtained with different filters.

  • Detector temperature

  • Right ascension

  • Declination

  • Exposure time

  • Focal length

Finder: Right Ascension Search Attribute
Finder: Right Ascension Search Attribute

Combining multiple queries

Often a search requires more than one set of criteria to reduce the number results to just those you are interested in. Finder window searches let you specify as many parameters as you want. Say you want to search for all light exposures of 1800 seconds taken through an OIII filter. To do this, you could select Filter name in the the first menu and have it match “OIII”. Click on the + button in the search bar to add another search parameter, set it to Image type and enter “light”. Then add another with the + button, select Exposure time and enter “1800”. Spotlight will display all images matching these criteria.

Finder: Combining Search Queries
Finder: Combining Search Queries

You can also change the operators of your criteria, e.g. is greater than instead of equals. This way, by combining criteria, you can even search for all images within a range of Right Ascension and Declination values.

You can use quotes to specify that a search should look at the exact phrase you type. You can also use Boolean search terms, to exclude criteria or to create an OR search. Once you have one condition set up, you can add a Boolean term to your next condition by Option-clicking the + button. The + will turn into an ellipsis (), and you’ll get a new pull-down menu with options for Any (OR), All (AND), or None (NOT).

Saving searches for later

To save your search as a Smart Folder, click on the Save button in the search bar and enter a name for the Smart Folder. Enable the Add To Sidebar option if you want add the Smart Folder to the sidebar of your Finder window. Whenever you open this Smart Folder, Spotlight will run the search again and update the results with all files that fit the criteria.

You can change the search by opening the Smart Folder, clicking the action button, and selecting Show Search Criteria.

Spotlight indexing should be enabled for the drive your images reside on. To check the Spotlight indexing status of a drive, open Terminal (in /Applications/Utilities), and enter

mdutil -s <path to volume>

For example,

mdutil -s "/Volumes/Macintosh HD"

It should return Indexing enabled. If you have your images on an external drive or NAS, then it may report Indexing and searching disabled. You can enable it with the same command (enter mdutil for the available options).

Acorn Plugins

Acorn by Flying Meat Inc. is a powerful image editor for macOS that supports nondestructive levels, curves and filters, layer masks, batch editing and many tools that work on pixels, text and shapes. It supports images with 8, 16 and 32 bits per channel. And you don’t need a subscription. It is a cost-effective solution for post-processing astronomical images.

Code Obsession’s Acorn Plugins add FITS, XISF and SBIG image support to Acorn. After installing the plugins, you can open any such image as easy as a JPEG or TIFF. They are a great addition to Observatory’s Quick Look and Spotlight plugins for the same image formats.

Calibrate, align and stack your images in Observatory, export as 32 bits FITS, open in Acorn and start post-processing. Add layers, annotations, watermarks. The options are endless.

What You Need

  1. Observatory.

  2. Acorn 5.6.5 or later. You can buy it direct or from the Mac App Store. The direct version has a 14 day trial period.

How to Install

  1. Choose Observatory ▸ Install Extras….

  2. Select a destination folder, for example the Desktop and choose Save. This results in an Extras folder on your Desktop.

  3. Open this folder and select the three files inside its Acorn Plugins folder.

  4. Start the Acorn application.

  5. Choose Help ▸ Open Acorn’s App Support Folder.

  6. Drag the three files (FITSACIO.acplugin, XISFACIO.acplugin and SBIGACIO.acplugin), into the Plug-Ins subfolder of Acorn’s Application Support folder. Remove the Extras folder from the Desktop afterwards.

  7. Quit the Acorn application (Acorn ▸ Quit Acorn).

  8. Start the Acorn application once again.

There’s a video on our website that demonstrates these steps.

How to Use

With these plugins installed, you can open FITS, XISF and SBIG images in Acorn, drag & drop them onto its application icon, and use the Image ▸ Open Master With ▸ Acorn option in Observatory. To avoid accidentally overwriting the files, the plugins do not allow you to save them in these formats.

The plugins automatically set Image ▸ Image Depth to 32 Bits Per Channel (Really Deep Color) when opening any such image. To improve performance and reduce disk space usage, you may want to change this to 16 Bits Per Channel (Deep Color).

Because of the dynamic range of astronomical images, one of the first things you will usually do is adding nondestructive levels (Image ▸ Levels…) and curves (Image ▸ Curves…). You might want to use multiple of these to get the desired results.

Save the edited image in Acorn’s default .acorn format. When you’re happy with your image, just export it into a more common format, like JPEG.

Unlike Observatory, the Acorn Plugins have no automatic update mechanism. Keep an eye on their Release Notes or the Blog. Observatory will notify you about updates, and you can also use an RSS reader to follow the blog.

If you have questions about the plugins, please contact us. For questions about Acorn, please contact Flying Meat Inc.

Acorn Plugins by Code Obsession
Acorn Plugins by Code Obsession

Preferences

To open Observatory’s preference window, choose Observatory ▸ Preferences, or use the keyboard shortcut (⌘,). There are four preference panes that you can use to further customize Observatory to suit your needs.

General Preferences

General Preferences
General Preferences

The General tab of the Preferences window includes settings for common interactions you’ll have with Observatory. It contains the following preferences:

  • Compute device

    Observatory is capable of using a Graphics Processing Unit (GPU) instead of the Central Processing Unit (CPU) for many intensive computations. Depending on the available hardware, this can result in a profound speedup of these computations.

    This preference lists the supported compute devices on your system, which typically consist of a single CPU and one or two GPUs. The CPU is selected by default. The GPU that is currently connected to your display is indicated with an icon (🖥) next to its name. You should generally not select the GPU that is connected to the display, as this will impact the overall system performance.

Stacking, calibration and the star detector, used internally by the plate solver and the align adjustment, all optionally use a GPU for their computations. It may not always lead to a performance improvement, so use this option with caution.

  • Sidebar icon size

    The second preference is to adjust the size of the icons and text in the sidebar. The default is the size you have configured in the General tab of your System Preferences. You can override it here.

  • Reset Warnings

    If you selected “Do not show this message again” in one or more dialogs, clicking Reset Warnings makes the messages appear again.

Accounts Preferences

The Accounts tab of the Preferences window includes settings for the Virtual Observatory.

The Virtual Observatory is used to search for and download images from several professional astronomical image archives. To download images from the ESO archive a user account is required. Creating it is free, and can be done at http://www.eso.org/userportal/. On that page, select I would like to create a new account, and follow the instructions.

After you have created the account, enter your ESO User Portal username and password here. The account information is securely stored in your computer’s keychain and only transmitted to eso.org over a secure connection. It is never transmitted to us or anyone else.

Accounts Preferences
Accounts Preferences

Catalogs Preferences

The Catalogs tab of the Preferences window includes settings for optional astronomical catalogs that enhance the astrometrical matching capabilities of Observatory.

Although Observatory comes with the highly accurate Tycho–2 catalog of more than 2.5 million of the brightest stars up to magnitudes V~11, for many astronomical images this is not enough for finding an astrometrical match. Hence Observatory can be augmented with the UCAC4 and USNO-A2.0 catalogs.

Catalogs Preferences
Catalogs Preferences

UCAC4 is a catalog of 113,780,093 stars covering the entire sky, mainly in the 8 to 16 magnitude range in a single bandpass between V and R with positional errors of about 15 to 20 milliarcseconds. It is more accurate than the USNO-A2.0 catalog, and is preferred over it for astrometric matching. Observatory does not automatically download this 9GB catalog for you. Instead, you will need to do this manually from http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/322A into a folder anywhere in your file system. After completing the download, this folder should then contain a UCAC4 folder that looks like this:

Finder - UCAC4
Finder - UCAC4

Now click the Select Folder… button of the UCAC4 Catalog section in the preferences, and select this UCAC4 folder.

The easiest way to download the data is to use an FTP client. Cyberduck (http://cyberduck.io/) for example, which is Open Source and can be downloaded for free by clicking the “Download for Mac” button on their website.

After installing the FTP client, open the UCAC4 catalog page in Safari and click the “FTP” tab. It will then automatically open the FTP connection using Cyberduck at the correct path (/pub/cats/I/322A) on the FTP server. Select all the files listed, including the UCAC4 folder, and click “Download To…” of Cyberduck’s menu. It’s 9GB of data, so the download will take a while.

Note that although Safari has some support for FTP, it will not work in this case because it is unable to resolve the UCAC4 link on this FTP server.

USNO-A2.0 is a catalog of 526,280,881 stars covering the entire sky, down to magnitude 19. The catalog can be downloaded from ftp://ftp.nofs.navy.mil/pub/outgoing/usnoa/ and requires approximately 7GB of disk space. Assuming you have downloaded it into a folder named USNO-A2.0, it will look like this afterwards:

Finder - USNO-A2.0
Finder - USNO-A2.0

Now click the Select Folder… button of the USNO-A2.0 Catalog section in the preferences, and select this USNO-A2.0 folder.

In the end, your Catalogs Preferences will look something like this:

Catalogs Preferences Example
Catalogs Preferences Example

You can now use both catalogs for astrometric matching, and overlay them onto your images.

Export Preferences

The Export tab of the Preferences controls how images are exported.

When you export images, you are presented with a number of presets for the output image format, the naming of the exported files as well as the generated folder structure. You configure these presets here. You can modify the default ones, or add and remove presets according to your needs.

Export Preferences
Export Preferences

Working in Observatory

Although you can create a single library for all your images by just dragging the folder on top of the Observatory application icon, which allows you to view their metadata, organize them in albums without the fear of modifying the original data, and focus on them by object category, there’s much more you can do with Observatory.

Here are some ideas to get started.

Quickly organize your images with the Finder

Because macOS doesn’t know what a FITS, XISF or SBIG file is, after acquiring images they all are displayed as generic icons in the Finder. Wouldn’t it be nice if you could at least see actual thumbnails, full previews and image metadata directly in the Finder?

With Observatory you will, because it includes Quick Look and Spotlight plugins for FITS, XISF and SBIG files. They work quietly in the background, and you don’t even need to run Observatory itself for this to work.

In the Finder, but also in Open/Save Dialogs of any application, these images are now displayed as thumbnails. You can take a closer look by pressing spacebar and view select metadata in the Finder with Get Info (⌘I). You can also use Spotlight to find images. Not just by file name, but also by exposure date, image type, dimensions, exposure duration, focal length, detector temperature, filter name, equatorial coordinates and many more attributes found in your images.

Check the images of last night’s imaging session

When you wake up the next morning, drag the folder containing the images of last night’s imaging session and drop it onto the Observatory application icon.

After a few seconds, you will be presented with a window containing all the images and see their metadata. Here you can quickly visually inspect them, determine FWHMs and reject those you dislike by choosing Stack ▸ Reject (⌃⌘0).

When you’re done, select the rejected ones and choose Image ▸ Show Master in Finder. A Finder window opens with the rejected images selected. There you can opt to drop them in a separate folder (New Folder with Selection), or move them to the trash all together.

Afterwards, you can just close the Observatory window, without even saving the newly created library.

Create a library for prospective targets

While preparing an imaging session for a list of targets, why not create a library, and use Virtual Observatory to download each target’s images from the DSS, SDSS, PTF or other archives? It may lead you to other interesting objects nearby.

Each target having its own library

Create a library for each target object, collecting observations spanning multiple observation sessions. Add master calibration frames, calibrate, align, and stack the images. Plate solve the stacked image, overlay astronomical catalog data, and export the image for post processing. Save the library to maintain a processing history.

A library of calibration frames

Use a library to collect all your calibration frames, auto-stack them, quickly inspect individual images using the blink animation, and export them as master calibration frames in 32 bit floating point FITS format. Use Observatory’s powerful export feature with folder and file naming templates to ensure that your master calibration frames are exported with consistent naming.

Research projects

For example, create a “Kuiper belt” library, add folders for individual objects and in each folder add albums with observations obtained through various instruments. Add your own observations and research images obtained through Observatory’s Virtual Observatory feature. Attach research papers to albums and individual images, add notes, tags and color code them.

Did anything change?

There’s a goldmine of raw image data available through Virtual Observatory. Align and blink some with your image. If your image is plate solved, it only takes one keystroke to take you there (⌃⇧⌘F).

Organize your images with the Finder even more

Quick Look and Spotlight are great, but you are still manually grouping the images with the Finder, based on their timestamp, type or target. Observatory can help you to make that easier too, and it doesn’t care if you forgot to update your settings during acquisition and all your files are named 00000127.DARK.FITS, 00000128.DARK.FITS, ….

Drag the folder with the images and drop it onto the Observatory application icon. Select them all in the Observatory browser, and choose Image ▸ Move to New Album. While they are still all selected, choose Stack ▸ Auto-Stack.

Now your images are grouped by their timestamp, type, filter name, CCD temperature, etc. They didn’t get organized like this in the Finder though. To do that, select one stack, click Stack ▸ Unstack (⌃⌘U), and choose Image ▸ Show Master in Finder. In the Finder window that opens, choose New Folder with Selection. Repeat this for each stack.

Afterwards, you can just close the Observatory window, without saving.

Convert images

If you have an old folder full of SBIG images, you can easily convert them all to the FITS format.

Drag the folder with the images and drop it onto the Observatory application icon. Select them all in the Observatory browser and choose File ▸ Export ▸ Master Image…. Select the destination folder and click the Export button to start the export.

Observatory’s export capabilities actually go well beyond this. You can export to many more image formats, resize images during exporting, use file naming templates and more.

Here is an exhaustive list of every single menu item, along with any corresponding keyboard shortcut, available in Observatory.

If you find a menu option that doesn’t have a keyboard shortcut but you really want one, you can always define new ones in the Shortcuts tab of  ▸ System Preferences ▸ Keyboard.

The Observatory menu holds commands related specifically to the administration of the Observatory application itself. View and modify your preferences here.

  • About Observatory

    Find out some details about your copy of Observatory. This is good for checking exactly which version you’re using.

  • Preferences… (⌘,)

    Open the Observatory preferences window, where you can customize how the application works for you.

  • Install Extras…

    Install the Acorn Plugins.

  • Services

    Access system-wide macOS services offered by other applications.

  • Hide Observatory (⌘H)

    Temporarily hide all of Observatory’s windows.

  • Hide Others (⌥⌘H)

    Temporarily hide windows of all other applications so you can concentrate on Observatory.

  • Show All

    Show all windows of all applications.

  • Quit Observatory (⌘Q)

    Stop using Observatory and put it away for now. Your libraries are automatically saved.

The File menu contains commands related to Observatory on a library level. Create or open a library, import images into it or export images from it.

  • New Library

    Create a new empty Observatory library document.

  • Open… (⌘O)

    Open an existing library document.

  • Open Recent

    Observatory keeps track of recently opened library documents and includes their names in this menu so you can reopen a library and continue your work.

  • Close (⌘W)

    Close the frontmost window. Even if you close the last remaining Observatory window, you can always just open a new one.

  • Save (⌘S)

    Save the contents of the current library document.

  • Duplicate (⇧⌘S)

    Create a duplicate copy of the current library document. The exact contents of the current window are copied into a new window, which has the filename in the titlebar highlighted so you can enter a different name for the file. The file will be saved in the same location as its parent.

  • Rename…

    Choose this option to highlight the filename in the document’s titlebar so you can enter a new name for the file.

  • Move To…

    Choose this option to open a sheet and select another location on your Mac to store the file.

  • Revert To

    Opens Time Machine so you can sift through earlier saves of the current library document and restore it from an older save.

  • Import

    This submenu contains commands related to importing images into the library and managing Source Folders. The Source Folder Panel’s action and contextual menus provide shortcuts to these commands.

    • Images… (⇧⌘I)

      Import images into the library. If the library is empty, you will be asked to either import a whole folder of images, or add source folders first.

    • Add Source Folder…

      Because of macOS imposed sandbox restrictions, Observatory needs to be given access to the folders containing your images. Choose this command to give Observatory access to a folder and add it to the Source Folder Panel.

    • Remove Source Folder…

      Remove the selected source folder from the Source Folder Panel and all its image versions from the library. This will not remove the folder or its images from the file system.

    • Show Source Folder in Finder

      Open a Finder window for the selected folder.

    • Locate Source Folder…

      The references to Source Folders are stored such that renaming or moving them on the same disk will usually not break the link. If you move it to another disk, the link will be broken though. The master images will then not be accessible to Observatory. To make them accessible again, choose this command and select the new location of the Source Folder.

  • Export

    Export your images in a variety of formats. You can use one of the default file formats, file naming templates and folder naming templates, or define your own using the Export Preferences.

    • Image… (⇧⌘E)

      Export the image versions currently selected in the Browser.

    • Master Image…

      Export the master version of the images currently selected in the Browser.

    • Managed Master…

      Export the managed master image of your selection. Images you import from your file system are referenced by Observatory, not copied into the library document. Images you download using Virtual Observatory are stored in the library itself though, and this menu item gives you the ability to copy this original file into your file system.

  • Export as PDF…

    Create a PDF file from the images you have selected in the Browser. Each image, its version name, basic metadata and the notes is added to a separate page in the PDF. If the image is Matched, it optionally includes the overlays.

  • Compact Library…

    Removes all generated thumbnails and unused helper files from the library. They will be regenerated when needed. Use with caution as regenerating them requires reading the master images, and regenerating all stack thumbnails may slow down your system.

If you press the (option) key while selecting the File ▸ Compact Library… menu item, it will change into Optimize Library…. Choose this menu item if you wish to immediately generate the thumbnails of all images in a library.

  • Empty Trash…

    Permanently remove all images and albums that were moved into the trash.

  • Stop Tasks… (⌘.)

    Gracefully stop image loading, processing and stacking, and deselect all currently selected images. Observatory sometimes automatically initiates such tasks in the background as well, and this menu item also stops these. In addition, it will temporarily stop Observatory from initiating new background tasks.

  • Page Setup… (⇧⌘P)

    Open the standard macOS Page Setup window, where you can change some settings for printing (or exporting to a PDF file). These settings are saved even if you quit Observatory.

  • Print… (⌘P)

    Open the standard macOS Print window, with a variety of options for printing (or creating a PDF file).

  • Undo (⌘Z)

    Reverse the most recent change you made.

  • Redo (⇧⌘Z)

    Reenact the last change you undid.

  • Cut (⌘X)

    Remove the selected text or items, putting them on the clipboard so you can paste them somewhere.

  • Copy (⌘C)

    Put a copy of the selected text or items on the clipboard, so you can paste them somewhere.

  • Paste (⌘P)

    Take whatever’s on the clipboard and insert it at the current selection.

  • Paste and Match Style (⌥⇧⌘V)

    Ignore any styles on the text you’re pasting and just use the style already there at the place you’re pasting into. Of course, this only makes a difference in notes, since that’s the only place where you can have special styles anyway.

  • Delete

    Remove the selected text.

  • Select All (⌘A)

    If you are editing text, select it all, or if you are working with the Browser, select all items in the Browser.

  • Insert Time Stamp

    Automatically type the current date or time, as defined by the Short Date, Long Date, and Time formats set up in System Preferences’ Language & Region pane. This can be handy when editing image, stack or album notes.

    • Short Date

    • Short Date and Time

    • Time

    • Long Date

    • Long Date and Time

  • Find

    This submenu contains the standard Find commands included in many macOS applications. In Observatory they are handy when editing image, stack or album notes.

    • Find… (⌘F)

    • Find and Replace… (⌥⌘F)

    • Find Next (⌘G)

    • Find Previous (⇧⌘G)

    • Use Selection for Find (⌘E)

    • Jump to Selection (⌘J)

  • Format

    This submenu contains standard macOS commands that apply to text in image, stack or album notes.

    • Font

      This submenu contains commands to change the typeface and style of your text.

    • Text

      This submenu contains alignment options for text.

    • Spelling and Grammar

      This submenu contains the standard Spelling commands for the macOS spell checking system.

    • Substitutions

      Use this submenu to enable or disable automatic text and punctuation substitutions.

    • Transformations

      This submenu contains commands that apply to selected text to convert it to completely upper case, lowercase, or capitalize each selected word, respectively.

    • Speech

      This submenu contains the Start Speaking and Stop Speaking commands, which you can use to make the macOS text-to-speech system say the selected text out loud.

  • Start Dictation

    With dictation enabled in  ▸ System Preferences ▸ Keyboard ▸ Dictation, select an editable text field and use this command to enter text via the spoken word.

  • Emoji & Symbols (⌃⌘Space)

    Open the macOS Character Palette, where you can find characters not easily accessible from the keyboard

  • Actual Size (⌘1)

    Scale your image in the current editor to 100 percent (normal size).

  • Zoom to Fit (⌘9)

    Scale your image in the current editor to make it completely visible in the window, regardless of its size.

You can use the zoom gesture to magnify and demagnify the view of your image. You can also quickly toggle between zoom levels by using the smart zoom gesture. The smart zoom gesture is a two-finger double tap on trackpads.

  • Zoom In (⌘+)

    Magnify the view of your image in the current editor. You can scale your image up to 1600 percent.

  • Zoom Out (⌘-)

    Demagnify the view of your image in the current editor. You can scale your image down to approximately 6 percent.

  • Inverted

    Display the image in the current editor with inverted colors.

  • Show/Hide Rulers

    Show or hide the rulers, with the origin at the bottom left, and using pixel units.

  • Image Type

    Images displayed in the browser can be filtered by image type. Choose here, or using the corresponding Image Type Filter in the browser if and how you want to reduce the number of displayed images.

    • All

      Display all images, regardless of their type.

    • Bias

      Display only bias calibration images, which are those with an image type that contains “Bias”.

    • Dark

      Display only dark calibration images, which are those with an image type that contains “Dark”.

    • Flat

      Display only flat calibration images, which are those with an image type that contains “Flat”.

    • Light

      Display only those images that have an image type that contains “Light”.

    • Other

      Display only those images that have an image type that neither contains “Bias”, “Dark”, “Flat” or “Light”.

  • Columns

    Choose here which columns you want the List Browser to display. The selection is coupled to the above View ▸ Image Type selection. For example, unless you change it, Observatory doesn’t display the Duration column when the Bias Image Type Filter is enabled, but it does so for all other Image Type Filters.

    • Name

    • Badges

    • Color Labels

    • Rating

    • Status

    • Image Type

    • Duration

    • Binning

    • Canvas Size

    • Filter Name

    • Pixel Size

    • CCD Temperature

    • Constellation

    • Center Right Ascension

    • Center Declination

    • Center Azimuth

    • Center Altitude

    • Telescope

    • Focal Length

    • Aperture Diameter

    • Aperture Area

    • Camera

    • Guider

    • Observer

    • Observatory

    • Import Date/Time

  • Subtitle

    Choose here which information you want the Image Browser and Image Strip Browser to display below the image name. The selection is coupled to the above View ▸ Image Type selection. For example, unless you change it, Observatory doesn’t display the Duration when the Bias Image Type Filter is enabled, but it does so for all other Image Type Filters.

    • Rating

    • Status

    • Image Type

    • Date/Time

    • Duration

    • Binning

    • Canvas Size

    • Filter Name

    • CCD Temperature

    • Focal Length

    • Aperture Diameter

  • Sort By

    Choose here how you want the Browser to sort the displayed images. In the List Browser, you can change the sorting also by clicking the column titles. The selection is coupled to the above View ▸ Image Type selection.

    • Name

    • Color Label

    • Rating

    • Status

    • Weight

    • Image Type

    • Date/Time

    • Duration

    • Filter Name

    • Center Right Ascension

    • Center Declination

    • Import Date/Time

    • Ascending

      Use ascending sorting.

    • Descending

      Use descending sorting.

  • Show/Hide Matched

    Show or hide images that have been Matched.

  • Show/Hide Rejected

    Show or hide images you have rejected.

  • Show Browser Only (⇧⌘⏎)

    Show only the Browser in the center of Observatory’s library window.

  • Show Browser & Editor (⌥⌘⏎)

    Show the Editor and Browser at the same time in the center of Observatory’s library window.

  • Show Editor Only (⌘⏎)

    Show only the Editor in the center of Observatory’s library window. Make sure to first select one or more images in the Browser beforehand, or it will be empty.

  • Show Virtual Observatory (⇧⌘F)

    Changes the center of Observatory’s library window into that of the Virtual Observatory. Here you can search the vast online archives of astronomical images taken with the telescopes of professional observation sites. You can import them directly into Observatory.

If you press the option key while selecting the Show Virtual Observatory menu item, it will change into Match Virtual Observatory (⌃⌥⌘F). If your currently selected image is Astrometric Matched, the Virtual Observatory will then use its center equatorial coordinates to initiate a search right away. This is handy way to search for images in the archives that cover the same area as your current image.

  • Sidebar

    This submenu contains commands related to the Sidebar along the left edge of Observatory’s library window.

    • Show/Hide Preview

      Expand or collapse the Image Preview Panel.

    • Show/Hide Source Folders

      Expand or collapse the Source Folder Panel.

    • Show/Hide Sidebar (⌘0)

      Choose whether to display the left sidebar that contains the Library Navigator, Image Preview and Source Folders.

  • Editor

    This submenu contains commands related to the Editor in the center of Observatory’s library window.

    • Standard

      Show only the standard editor.

    • Assistant

      Show the assistant editor next to the standard editor.

    • Add Assistant Editor

      Add an assistant editor below the existing assistant editors.

    • Remove Assistant Editor

      Remove the current assistant editor.

    • Reset Editor

      Remove all assistant editors but one.

    • Focus Next Editor (⌥⌘`)

      Make the next editor the active one.

    • Focus Previous Editor (⌥⇧⌘`)

      Make the next previous editor the active one.

    • Go Back (⌘[)

      Show the previous image of your browser selection in the editor. Only enabled if you have more than one image selected in the browser.

    • Go Forward (⌘])

      Show the next image of your browser selection in the editor. Only enabled if you have more than one image selected in the browser.

    • Play/Pause Animation

      Loop through the images selected in the browser and display each in the editor.

  • Browser

    This submenu contains commands to switch between the different types of Browsers.

    • Image Strip

      Switch to the Image Strip Browser.

    • Image

      Switch to the Image Browser.

    • List

      Switch to the List Browser.

  • Inspectors

    This submenu contains commands related to the Inspectors along the right edge of Observatory’s library window.

    • Version

      Switch to the Version Inspector.

    • Layer Adjustments

      Switch to the Layer Adjustments Inspector.

    • Measure

      Switch to the Measure Inspector.

    • Stack

      Switch to the Stack Inspector.

    • Album

      Switch to the Album Inspector.

    • Show/Hide Attachments

      Expand or collapse the Attachments Pane.

    • Show/Hide Channels

      Expand or collapse the Channels Pane.

    • Show/Hide Layers

      Expand or collapse the Layers Pane.

    • Show/Hide Histogram

      Expand or collapse the Histogram Pane.

    • Show/Hide Inspectors (⌥⌘0)

      Summon up the inspectors, or put them away.

  • Show/Hide Toolbar (⌥⌘T)

    Show or hide the toolbar.

  • Customize Toolbar…

    Choose which controls appear in the library window’s toolbar.

  • Enter Fullscreen (⌃⌘F)

    View Observatory at the full dimensions of your screen, or return it to a modest window.

  • New Album (⌘N)

    Create a new empty Album. If chosen while a folder has been selected in the Library Navigator, the Album is created inside that folder. To create an Album at the root level, select “All Images” first.

  • New Folder (⇧⌘N)

    Create a new empty Folder. If chosen while a folder has been selected in the Library Navigator, the new Folder is added as a subfolder. To create an Folder at the root level, select “All Images” first.

  • New Smart Album (⌥⌘N)

    Create a new Smart Album. A sheet opens in which you can set the criteria. If chosen while a folder has been selected in the Library Navigator, the Smart Album is created inside that folder. To create an Smart Album at the root level, select “All Images” first.

  • Edit…

    Edit the name of an Album or Folder, or in case of a Smart Album, edit its criteria. You can also edit the name by clicking on it in the Library Navigator while the collection is selected, or by using the Album Inspector.

Collections of the same type and at the same folder level, must have unique names.

  • Edit Note… (⌘’)

    Although you can add, view or edit an image or stack note using its corresponding inspector, it is more convenient to use the much bigger sheet that this menu item provides.

  • Lock/Unlock

    Lock or unlock a collection to prevent further changes.

  • Attach File…

    Choose a file to attach to the folder, album or smart album that is currently selected in the Library Navigator.

  • Duplicate

    Duplicate an Album or Smart Album. In case of an Album, all its images and Stacks are duplicated as well.

  • Add To Favorites

    If you mark a collection as a favorite, it will be added to the Favorites item in the Library Navigator. All images of an Album will implicitly be marked as favorite, including those you will add later to it. If you wish to mark a single image as favorite, you should choose Image ▸ Add To Favorites instead.

  • Remove From Favorites

    Remove a collection from the favorites item of the Library Navigator.

  • Move To Archive

    Move a collection to the Archive. This makes it invisible to Smart Albums and the Library Navigator search.

  • Move To Trash

    Move a collection to the Trash.

  • Put Back

    Restore a collection from the Archive or Trash.

  • Hide/Unhide Album

    Hide a collection from the Library Navigator and make it invisible to Smart Albums and the Library Navigator search. You can unhide a collection by first having the Library Navigator display all hidden collections, and then unhide it.

  • Show/Hide Hidden

    Show all hidden collections in the Library Navigator, or hide them again.

A stack is set of images, all part of the same album and each with an associated weight. Usually these are images of the same object, or the same calibration image type, with the intend to combine them. Every stack has an associated “Stack Image”, which is the result of combining the images within the stack. To further process a Stack Image, one first has to create a Managed Master from it.

  • Stack (⌃⌘S)

    Creates a stack of the selected images. The selected images all have to belong to an album, the same album, in order for you to stack them. You cannot stack images in the Inbox.

    If you create a stack of images, it initially creates a stack image with one layer for each selected image. If you switch to one of the other stack types using the Stack Inspector, it will combine the images into a single layer. Use this to create master calibration images, or to combine images of the same object to reduce noise.

  • Unstack (⌃⌘U)

    Unstack the selected images. They will remain part of the same album.

  • Auto-Stack

    Creates one or more stacks of the selected images. The selected images all have to belong to the same album. Observatory automatically groups them in stacks, using the following criteria:

    • Equal color mode (grayscale or RGB)
    • Equal number of layers
    • Equal image type
    • Equal canvas size
    • Equal filter name
    • Equal exposure duration
    • Equal binning values
    • Nearly the same CCD temperature (±0.5 ℃)
    • Nearly the same right ascension and declination, if available (± 0.1 °)
  • Pick (⌃⌘8)

    Selects the pick image of the stack. The pick image is usually the most representative or best image of the stack, e.g. the sharpest one. It is referenced by some (if used) layer adjustments of other images in the same stack. Every stack has a pick. When a stack is created, or when you unstack a pick image, the earliest exposure in the stack is set as its pick image.

  • Promote (⌃⌘=)

    Increases the weight of the selected images with an amount that is dependent on the number of selected images. The maximum weight is 100 %. This menu item is only enabled for stacks.

  • Demote (⌃⌘-)

    Decreases the weight of the selected images with an amount that is dependent on the number of selected images. The minimum weight is 0 %. This menu item is only enabled for stacks.

  • Accept (⌃⌘1)

    Sets the weight of the selected images to 100 %.

  • Reject (⌃⌘0)

    Sets the weight of the selected images to 0 %. If part of a stack, the image is ignored for the creation of the stack image.

  • Auto-Weight

    Adjusts the weight of the selected images based on a property of the image contents. This menu item is only enabled for stacks.

    • Background

      The weight is based on the average background value of the whole image. The images with the lowest background value are assigned the highest weight.

    • FWHM

      The weight is based on the average FWHM of the stars in the image. The sharpest images (small FWHM) are assigned the highest weight.

    • FWHM (brightest)

      The weight is based on the FWHM of the brightest star in the image. The sharpest images (small FWHM) are assigned the highest weight.

    • Star Peak

      The weight is based on the average peak value of stars in the image. The images with the highest peak values are assigned the highest weight.

    • Star Peak (brightest)

      The weight is based on the the peak value of the brightest star in the image. The images with the highest peak values are assigned the highest weight.

  • Select

    This submenu contains commands to quickly select images when the browser is focused on a stack. Each has a corresponding button in the center of the browser focus bar. You typically choose the third button to quickly select all the stack’s images and apply the same layer adjustments to each, and then check the results in the editor using its Play/Pause button. You can quickly inspect the final stacked image by choosing the first button.

    • Stack

      Selects the stack image.

    • Pick

      Selects the stack’s pick image.

    • All Items

      Selects all images that comprise the stack.

  • Focus on Stack (⌃⌘[)

    Focus the browser on the selected stack, revealing the images comprising the stack.

  • Unfocus (⌃⌘])

    Focus the browser on the currently focused stack’s album, or the parent of the currently focused folder, album, or smart album.

  • Edit Note… (⌘’)

    Although you can add, view or edit an image or stack note using its corresponding inspector, it is more convenient to use the much bigger sheet that this menu item provides.

  • Resize Canvas…

    When you import an image into Observatory, the canvas size of the image is the same as the image dimensions. When you apply layer adjustments to it, or when you combine images in a stack, you may wish to change the canvas size by choosing this menu item.

  • Match… (⌃⌘M)

    Displays a sheet to Astrometric Match the selected image. Astrometric Matching is a process to relate image pixels to sky coordinates. Observatory will use information from the selected images to set the initial values in this sheet.

If you press the option key while selecting the Image ▸ Match… menu item, it will change into Match With Master… (⌃⌥⌘M). The initial value in the Astrometric Matching sheet will then not be based on the current image version, but on the master. This can be useful if you made incorrect changes to the version’s metadata.

  • Unmatch

    Remove the information that Astrometric Match added to the image from it.

  • Lock

    Lock or unlock selected images. Locking an image prevents further modifications to it metadata and layer adjustments.

  • Attach File…

    Choose a file to attach to the selected images.

  • New

    • Version from Master

      Creates a new image version from the master of the selected image. The new image is like a clean original, without any layer adjustments applied to it.

    • Duplicate Version

      Creates a duplicate version from the selected image version. It is an exact duplicate, except for its name.

    • Master

      Creates a new Managed Master from the selected image version or stack. Because layer adjustments cannot be applied to a stack, creating a new managed master from it a stack is what you usually would do.

  • Mode

    • Grayscale

      Converts a RGB image into a grayscale image by combining its three channels into one.

    • RGB

      Converts a grayscale image into a RGB image by duplicating its single channel.

  • Focus on Album

    Select the album the selected images are part of in the Library Navigator and Browser.

  • Move To New Album

    Creates a new album and moves the currently selected images into this new album.

If you press the option key, the menu item will change into Add To New Album. Instead of moving the images into the newly created album, this will copy them instead.

  • Move To Album

    Moves the selected images to another album.

    The calibration albums “Bias Calibration”, “Dark Calibration” and “Flat Calibration” have a special function in Observatory and are used by the Calibrate Layer Adjustment. Any images added to these Albums will automatically get an image type of “MasterBias”, “MasterDark” or “MasterFlat” respectively.

If you press the option key, the menu item will change into Add To Album. Instead of moving the images into the album, this will copy them instead.

  • Remove From Album

    Removes the selected images from the currently selected Album in the Library Navigator. Removing an image from an Album moves it to the Inbox. If you want to remove it from the library, you should choose Image ▸ Move To Trash.

  • Add To Favorites

    If you mark an image as a favorite, the Favorites item in the Library Navigator will displays the image’s Album. Selecting it will only show its images you marked as favorite. If you wish to mark a whole Album as favorite, you should choose Album ▸ Add To Favorites.

  • Remove From Favorites

    Unmark an image as a favorite.

  • Move To Trash (⌘⌫)

    Moves an image to the Trash. It can be restored with Image ▸ Put Back as long as you didn’t choose File ▸ Empty Trash…. Even if you empty the trash, this only applies to the references to the master image if it resides outside the library. Observatory will never remove images from the actual file system.

  • Put Back

    Restores an image from the Trash. Images can be restored from the trash as long as you didn’t choose File ▸ Empty Trash…. Even if you did, master images that reside outside the library will never be removed by Observatory.

  • Reset Attributes…

    Completely resets all versions of a master, resetting all their metadata and erasing all layer adjustments. You would normally do this only if your master image was changed by another application.

  • Show Master FITS Header (⌥⌘I)

    If the master of the current selection is a FITS file, then you can choose this menu item to view and search in its FITS header.

  • Show Master in Finder

    Opens a Finder window with the folder in which the master image of the current selection resides, and select that master image. This menu item is not enabled for images that have a Managed Master, e.g. those that were downloaded using Virtual Observatory. If you wish to access those, you should choose File ▸ Export ▸ Managed Master… instead.

  • Open Master

    Opens the master of the selected image version with the default application.

  • Open Master With

    Opens the master of the selected image version with the chosen application.

  • Locate Master…

    If Observatory lost track of your master image, choose this to point it to the correct location. Before doing this, it is usually better to check your Source Folders first, and use **File ▸ Import ▸ Locate Source Folder…” to locate moved Source Folders.

The Layer menu contains commands related to the currently selected layer of an image. Add new layer adjustments here, or lock a layer to prevent modifications to it.

  • Calibrate

    Bias, dark and flat field correction. The relevant calibration images are taken from the Bias Calibration, Dark Calibration and Flat Calibration albums only. The layer dimensions, CCD temperature, exposure duration and filter name are taken into account for this. Archived calibration images are ignored.

    If you are not seeing the calibration frames you had expected, make sure that the relevant metadata matches.

  • Offset

    Reposition the layer.

  • Size

    • Double Size

      Double the size of the layer in both directions.

    • Half Size

      Reduce the size of the layer in both directions.

    • Resize

      Resize the layer in both directions using a scaling factor.

    • Binning

      Reduce the size of the layer in both directions by binning the pixels.

    • Pixel Aspect Ratio

      Adjust the pixel aspect ratio.

    • Crop

      Crop the layer to the given bounds.

  • Rotate

    • Mirror

      Reverse the layer’s left and right.

    • Flip

      Flip the layer upside down.

    • Rotate Left

      Rotate the layer 90° counterclockwise.

    • Rotate Right

      Rotate the layer 90° clockwise.

    • Rotate

      Rotate the layer at an arbitrary angle.

  • Stack

    This submenu contains layer adjustments that are only relevant to images which take part of a Stack. These adjustments are all relative to the Stack Pick.

    • Normalize

      Adjusts the pixel values of a layer such that its background or overall brightness matches that of the stack’s pick.

    • Align

      Align the layer with the stack’s pick.

  • Arithmetic

    Add a value to every pixel of the layer, subtract a value from every pixel of the layer, multiply a value with every pixel of the layer or divide every pixel with a value. Invalid (hot, missing) pixels are ignored.

  • New Layer

  • Duplicate Layer

  • Delete Layer

  • Show/Hide Layer

    Show or hide the current layer.

  • Lock/Unlock Layer

    Lock or unlock the current layer.

The Overlay menu holds commands related to the display of overlays in the editor, relevant only to matched images, i.e. images that use the World Coordinate System (WCS) to relate image pixels to sky coordinates.

  • Show/Hide Scale

    Draw the image scale onto you images.

  • Show/Hide Orientation

    Draw the image orientation onto you images.

  • Show/Hide Grid

    Draw an equatorial coordinate grid onto you images.

  • Show/Hide Messier

    Draw the positions of the objects in the Messier catalog with their B and V magnitudes, apparent size and orientation onto you images.

  • Show/Hide NGC/IC

    Draw the positions of the objects in the NGC/IC catalog with their B and V magnitudes, apparent size and orientation onto you images.

  • Show/Hide PGC2003

    Draw the positions of the galaxies in the PGC2003 catalog with their apparent size and orientation onto you images.

  • Show/Hide Tycho–2

    Draw the positions of the stars in the Tycho–2 catalog with their B and V magnitudes onto you images.

  • Show/Hide Solar System

    Draw the positions of the Solar System’s planets and Pluto onto you images.

  • More

    Show or hide other catalogs that are supported by Observatory, but not built-in.

    • Show/Hide UCAC4

      Draw the positions of the stars in the UCAC4 catalog with their R magnitudes onto you images. This menu item is only enabled if you have configured the UCAC4 catalog path in Observatory ▸ Preferences….

    • Show/Hide USNO-A2.0

      Draw the positions of the stars in the USNO-A2.0 catalog with their B and R magnitudes onto you images. This menu item is only enabled if you have configured the USNO-A2.0 catalog path in Observatory ▸ Preferences….

  • Show/Hide Catalog Labels

    Show or hide all catalog object name, magnitude, size and orientation labels.

  • Show All Overlays

    Show all the overlays, except those of the Overlay ▸ More menu.

  • Hide All Overlays

    Hide all the overlays.

When you have multiple library windows open in Observatory, use the Window menu to choose between them.

  • Minimize (⌘M)

    Shrink the frontmost window down into the Dock.

  • Zoom

    Switch the frontmost window between the biggest size possible and the last size you set.

  • Show Previous Tab (⌃⇧⇥)

    macOS Sierra and later support grouping windows from the same application into a unified window with tabs for each document (similar to the tabs used by most web browsers). With multiple Observatory libraries sharing a window in this way, this command navigates to a previous tab in the row.

  • Show Next Tab (⌃⇥)

    With multiple Observatory libraries sharing a window, this command navigates to the next tab in the row.

  • Move Tab to New Window

    If an Observatory library is displayed as a tab in a window with others, this command detaches the document’s tab into its own separate window.

  • Merge All Windows

    Move all currently open Observatory library windows into a single window with the documents separated by tabs.

  • Bring All to Front

    Get all of the Observatory windows up in front of other applications’ windows.

At the bottom of the Window menu is a list of all of your Observatory windows; choose one to bring it to the front.

Access a variety of support resources using the Help menu in Observatory, including this documentation, release notes, and contact with our friendly Support Humans.

  • Search

    Filter commands across all of Observatory’s menus to find and select a specific command.

  • Observatory Help

    View the help documentation available on our website.

  • Welcome…

    Display the Welcome window.

  • Blog

    Visit the Observatory Blog to see what’s brewing at our headquarters.

  • Videos

    Access the screencasts available on our website.

  • Release Notes

    View the Observatory release notes on our website.

  • Service and Support

    Visit the Observatory support page on the Code Obsession web site.

  • Contact Us

    Compose an email to the humans among the Observatory team. We’d be happy to give advice, answer questions, or just listen to your feedback.

Glossary

The following is an alphabetical list of terms you’ll encounter throughout the documentation, some of which may be unfamiliar or have special uses particular to Observatory.

Astronomy

  • 2MASS

    The Two Micron All-Sky Survey (2MASS) is a survey of the whole sky in three infrared wavebands around 2 micrometers.

  • ESO

    The European Southern Observatory (ESO) is a intergovernmental research organisation for astronomy. ESO has built and operated some of the largest and most technologically advanced telescopes. These include the New Technology Telescope (NTT), and the Very Large Telescope (VLT), which consists of four individual telescopes, each with a primary mirror 8.2 meter across, and four smaller auxiliary telescopes.

    Observatory can search and download images directly from the ESO Archive, including those obtained using the VLT (8.2 m), VST (2.6 m), VISTA (4.1 m), NTT (3.6 m) and the ESO 3.6 m telescope. If you have the right credentials, you can even download data that is still under the proprietary period.

  • DSS

    The Digitized Sky Survey (DSS) is a digital version of several photographic atlases of the night sky.

    DSS has two generations. Observatory can search and download both DSS-I and DSS-II images.

  • GOA

    Gemini Observatory Archive. The Gemini Observatory consists of two 8.19 m telescopes, the Gemini North in Hawaii and the Gemini South in Chile.

  • HST

    The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990, and remains in operation.

    Observatory can search and download images from the HST Mikulski Archive for Space Telescopes and Hubble Legacy Archive (HLA).

  • KOA

    The W. M. Keck Observatory is a two-telescope astronomical observatory near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes feature 10 m primary mirrors. Through the Keck Observatory Archive (KOA), Observatory provides access to the images obtained with the NIRC2 instrument.

  • Messier Catalog

    The Messier objects are a small set of astronomical objects first listed by French astronomer Charles Messier in 1771.

    Observatory can overlay the objects in this catalog onto your images.

  • NED

    The NASA/IPAC Extragalactic Database (NED) is an on-line astronomical database for astronomers that collates and cross-correlates astronomical information on extragalactic objects (galaxies, quasars, radio, x-ray and infrared sources, etc.).

    Observatory uses NED for its Virtual Observatory and Astrometric Matching.

  • NGC/IC Catalog

    The New General Catalogue of Nebulae and Clusters of Stars (NGC) is a catalog of deep-sky objects compiled by John Louis Emil Dreyer in 1888. It contains 7,840 objects. Dreyer published two supplements, known as the Index Catalogues (IC). They contain a total of 5,386 objects.

    Observatory can overlay the objects in this catalog onto your images.

  • PGC2003 Catalog

    This is a catalog containing 983,261 galaxies, all brighter than magnitude B∼18. Observatory includes the PGC2003 catalog, and can overlay the objects in it onto your images.

  • PTF

    Palomar Transient Factory Archive. A survey using the Palomar Samuel Oschin 1.22 m Schmidt Telescope.

    Observatory can search and download the level 1 images of this archive.

  • SDSS

    The Sloan Digital Sky Survey (SDSS) is a multi-filter imaging and spectroscopic redshift survey using a dedicated 2.5 m wide-angle optical telescope.

    Observatory can search and download the imaging catalog data of Data Release 12 (DR12), which is the final data release of SDSS-III.

  • SHA

    Spitzer Heritage Archive. The Spitzer Space Telescope is a 0.85 m NASA infrared-wavelength space telescope.

    Observatory can search and download the level 2 images of this archive.

  • SIMBAD

    SIMBAD (the Set of Identifications, Measurements, and Bibliography for Astronomical Data) is an astronomical database of objects beyond the Solar System.

    Observatory uses SIMBAD for its Virtual Observatory and Astrometric Matching.

  • Tycho–2 Catalog

    The Tycho–2 Catalog is a catalog of more than 2.5 million of the brightest stars. The catalog is 99% complete to magnitudes of V11.0 and 90% complete to V11.5. The Tycho–2 positions and magnitudes are based on the observations collected by the European Space Agency’s Hipparcos satellite.

    Observatory includes the Tycho–2 catalog and uses it for Astrometric Matching. It also has the ability to overlay the catalog onto your images. Although it is highly accurate, its use for Observatory’s Astrometric Matching is limited to wide field images only.

  • UCAC4 Catalog

    A catalog of 113,780,093 stars covering the entire sky, mainly in the 8 to 16 magnitude range in a single bandpass between V and R with positional errors of about 15 to 20 mas. UCAC4 can be downloaded and requires approximately 9GB of disk space.

    Observatory can use this catalog for Astrometric Matching. It also has the ability to overlay the catalog onto your images. Although it contains less stars then the USNO-A2.0 catalog, it is much more accurate.

  • USNO-A2.0 Catalog

    A catalog of 526,280,881 stars covering the entire sky, down to magnitude 19. USNO-A2.0 can be downloaded from ftp://ftp.nofs.navy.mil/pub/outgoing/usnoa/ and requires approximately 7GB of disk space.

    Observatory can use this catalog for Astrometric Matching. It also has the ability to overlay the catalog onto your images. Although it contains more stars then the UCAC–4 catalog, it is much less accurate.

  • WISE

    Wide-field Infrared Survey Explorer. WISE is a 0.4 m NASA infrared-wavelength space telescope.

    Observatory can search and download the images of the WISE AllWISE Atlas.

Image Processing

  • Bias Frame

    In addition to thermal noise, a CCD camera generates some noise due to its electronics that doesn’t change with exposure time. A bias frame records this noise.

    The image below is a bias frame taken with my ST–7XE NABG camera cooled at –20 °C. On this camera, the shortest possible exposure is 0.11 seconds, not 0 seconds, but it will do for a bias frame.

    Bias Image
    Bias Image

    At first glance, you may think that this camera is defective. Let’s take a closer look at this image:

    • Although the image looks really noisy, it has very little noise in it. I have enhanced the contrast by setting the black and white points for displaying the image to 90 and 130 respectively. The very brightest pixel in the entire frame is 176 units, and the very darkest is 55 units. Since this camera produces 16 bit grayscale images with 65,536 available brightness levels, and it adds a pedestal of 100 to every pixel to prevent negative values from occurring due to noise, the overall average brightness value of 105 means that at this temperature the camera produces very little noise. The low-level mottling effect across the entire frame is very small.

    • Another notable feature in this image is a gradient from left to right. The magnitude of the variations are very small, and this gradient is typical of many cameras. It occurs because of the time delay in reading across the chip. The pixels at left have a little more time to build up thermal noise, so they are brighter. The pixels at the left edge of the frame have an average value of 116. Pixels at the far right have an average value of 102. The gradient will occur in all frames, and is automatically dealt with when you reduce the images with dark, flat-field, and bias frames.

    As with all calibration frames, you will normally not apply a single one to your images, but combine many into a master bias and use that for calibration. This is because calibration also introduces some noise from the calibration frames themselves, and by using master calibration frames you minimize that. An example is a median combination of the above and 199 other bias frames taken in the same sequence:

    Master Bias Image
    Master Bias Image

    I have enhanced the contrast by using the same black and white points as before. Clearly the master bias is much less noisy than the single bias frame. You can now see a fine scale structure which is inherent to the CCD. You can also observe a few Hot Pixels.

  • Calibration

    The process of applying dark, bias, and/or flat field frames to light frames.

  • Centroid

    A star’s light is spread across several pixels by air turbulence and diffraction. The center is referred to as a centroid.

  • Dark Frame

    Records the dark current (also called thermal current) that occurs during an exposure of a given duration and temperature. It is taken with the shutter closed. The dark frame is subtracted from the light frame of the same duration and temperature to remove the dark current. If the dark and light frame do not match in duration, a bias frame can be taken to scale the dark frame, and allow it to be applied to the light frame.

  • FWHM

    The image of a star has a typical brightness profile as depicted below. The curve shows an idealized picture of the brightness levels of the pixels across a star image. With the brightest values at the top, this curve has most of the values falling near a central value (the centroid of the star image). There is no definite edge, but the Full Width at Half Maximum (FWHM) is a way to characterize the width of the star image. To find the FWHM, take the highest value, divide it by two, and measure the distance across the curve at that point.

    FWHM
    FWHM
  • Hot Pixel

    A bright pixel in an image caused by a pixel sensor with a higher than normal dark current.

  • Flat Frame

    An image which records the optical issues of your telescope and camera. Typically, the flat records vignetting as well as shadows from dust motes on your CCD and filters. By applying a flat frame, most of these optical issues can be cleaned up in your images.

  • Light Frame

    Also called an image. Taken with the shutter open.

Observatory

  • Album

    A type of container in the Observatory library that may contain images and stacks of images. Albums cannot be nested.

  • Badge

    A small icon Observatory places on an image in the browser to indicate that an adjustment, tag, or other change has been applied to it.

  • Browser

    The part of the Observatory interface that displays the contents of the currently selected Collection.

  • Collection

    A Folder, Album or Smart Album.

  • Editor

    An area in Observatory that displays the image currently selected in the Browser. You can use the Editor to perform adjustments on images as well as compare them with each other.

  • Focus

    See Primary Selection.

  • Folder

    A type of container in the Observatory library used to organize albums and smart albums. Folders can be nested.

  • Folder Format

    A naming convention that you can apply to destination folders when images are exported. Observatory provides a number of preset folder formats, and you can also create and save your own custom folder formats.

  • Image

    See Image Version.

  • Image Version

    An image you see and change in Observatory is called a Version. Versions are based on the original master, and you can change, copy, and adjust them any way you want. In Observatory, only versions are ever changed. The masters are never touched. A Version is like a recipe that is applied to its Master. It is a representation of the Master.

    Throughout Observatory and its documentation the term “Image” and “Version” actually is short for “Image Version”. Unlike a Master, a Version typically doesn’t take up much disk space.

  • Layer Adjustment

    A Layer Adjustment is a recipe applied to a Master. Each Layer has its own adjustments.

  • Library

    In Observatory, a container file that holds collections of images. The masters of these images may reside inside as well as outside this container file. You can have multiple libraries.

  • Managed Master

    A master that is stored inside the Observatory library itself. After its creation, it is never modified. Any changes to an image based on a managed master are applied to a Version of the master. A managed master has no corresponding source folder. Unlike regular masters, a managed master is permanently removed if all its versions are removed.

    You can export a Managed Master that was created by the Virtual Observatory by choosing File ▸ Export ▸ Managed Master…. This exports the original downloaded file.

    You can also create a Managed Master from an existing image or stack by choosing Image ▸ New ▸ Master…. You would typically only do this for a stack, and only if you want to apply Layer Adjustments to it. You cannot export such kind of Managed Master though, only a Version of it.

  • Master

    The source image that is referenced by Observatory. The master is never modified, so that the original image is preserved and can be used again. Anytime a change is made to the image, that change is applied to a Version of the master.

    When you import an image from your file system, it is not copied into the library, but a reference to it is stored in the library. Only when you download an image using the Virtual Observatory, it is copied into the library. The latter is named a Managed Master.

  • Master Version

    Immutable Version of the master image. It always exists if a master exists, but doesn’t count towards the number of versions of a master.

  • Match

    In Observatory, if an image is Matched, it can relate its image pixels to actual sky coordinates. For this it needs to know the center equatorial coordinates of the image, the projection used, and the transformation matrix. Observatory currently only supports Gnomonic (tangent plane, TAN) projections for Astrometric Matching.

    Masters may already contain all required information. For images that do not contain this information, Observatory can add it by choosing Image ▸ Match…. To make best use of all Observatory’s features, it is recommended to Match all images, except those that are for calibration only.

  • Name Format

    A naming convention that you can apply to images as they are exported. Observatory provides a number of preset name formats, and you can also create and save your own custom name formats.

  • Offline

    Images whose masters are currently unavailable to Observatory. Offline images appear in the Browser with a warning badge. Observatory currently does not support an offline workflow.

  • Pick

    A single image in a Stack that is referenced by layer adjustments of other images in the same stack. It is usually the most representative or best image of the stack, e.g. the sharpest one. Every stack has a Pick.

  • Primary Selection

    The most important image in an image selection. The image in focus in the current editor. The primary selection is identified by a thicker blue border. There can only be one primary selection in an image selection.

  • Rating

    In Observatory, the process of adding a value to an image to indicate its quality in relation to other images in a selection.

  • Smart Album

    Dynamic album in Observatory used to organize images by gathering them based on search criteria. Smart albums cannot be nested.

  • Source Folder

    A source folder represents a folder in the file system, outside of the Observatory library. Because the macOS Sandbox restricts access to the file system, you need to explicitly give Observatory permission to access the folders in which your images reside. Neither these folders, nor their contents, is ever modified by Observatory.

  • Stack

    A set of images, all part of the same album and each with an associated Weight. Usually these are images of the same object, or the same calibration image type, with the intend to combine them. Every stack has an associated “Stack Image”, which has no master, but is the result of combining the images within the stack. To further process a Stack Image, one first has to create a Managed Master from it.

    Creating a stack does not alter the original images. Use this to create master calibration images, or to combine images of the same object to reduce noise.

  • Tag

    A descriptive word about the subject in a collection or image. Collections and images can have multiple tags, some of which are automatically added by Observatory.

  • Version

    See Image Version.

  • Weight

    A property of each image version in the Observatory library that is used when combining multiple images. Images that are not part of a stack may only have a weight of 100% (accepted) or 0% (rejected). Images that are part of a stack may have any weight from 0% to 100%. The weights can be set manually or computed automatically.

FAQs

Does Observatory use a single library like Photos or iTunes?

No. An Observatory library is treated as a document. You can create as many different libraries as you wish, and have multiple open at the same time. You can even create temporary libraries which you do not explicitly save to disk, but discard after use.

When importing images into a new library, does Observatory copy all images?

No. Importing only copies the metadata of the images into the library. The library contains links to your images.

Can I rename image files or move them after I have imported them into a library?

Yes. As long as you do not move your files to another disk, you can rename and move them without breaking the links. And even if you do break the link, it is easy to restore it from within Observatory.

If I import the same folder twice, will this result in duplicate images?

No. During importing, Observatory computes an SHA1 hash of each image file and stores it along its metadata. This slows down importing, but ensures that you will never end up with duplicates, even if you rename or move images between imports.

Does Observatory support the images of my camera?

Observatory supports FITS, XISF (PixInsight), SBIG, DNG, NEF, CR2, TIFF, JPG, and many more image formats. It uses the system-level support for RAW images provided by macOS. The list of supported cameras can be found here:

https://support.apple.com/en-us/HT205272

We cannot guarantee that this list is up to date or correct though. If you are concerned whether it will support your files, then please try the demo or contact us before purchasing Observatory. Please refrain from sending images by email, but share one or more with us using for example Dropbox.

What are Observatory’s software and hardware requirements?

Observatory requires OS X 10.11 (El Capitan), macOS 10.12 (Sierra) or macOS 10.13 (High Sierra). A minimum of 4 GB RAM is required, and a SSD is highly recommended.

Observatory internally uses 32 bits floating point for each pixel in each channel. A 16 megapixel grayscale image expands to 64 MB in RAM, and a 16 megapixel RGB image to 192 MB. Observatory’s RAM utilization is not yet fully optimized, and currently it may use up to twice that for some images. If an image uses the calibrate adjustment, the calibration frames are loaded into RAM as well, and when stacking, all its images are loaded into RAM. The practical size of a stack is therefore limited by the available RAM.

Does Observatory take care of all my image processing needs, including stacking video clips of planets?

Observatory supports preprocessing pipelines for calibrating, normalizing, registering and stacking images. It still lacks postprocessing, and does not handle video clips. Observatory is an evolving product, and its initial focus is on organizing images, accessing online image archives, integrating the image formats used in astronomy with macOS, plate solving, and preprocessing.