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.
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.
Our Acorn Plugins.
Acorn Plugins.zip file in your Downloads folder, if not done automatically. This results in an
Acorn Plugins folder in your Downloads folder.
Open this folder and select the three files inside.
Start the Acorn application.
Choose Help ▸ Open Acorn’s App Support Folder.
Drag the three files (
SBIGACIO.acplugin), into the
Plug-Ins subfolder of Acorn’s Application Support folder. Remove the now empty
Acorn Plugins folder from Downloads afterwards.
Quit the Acorn application (Acorn ▸ Quit Acorn).
Start the Acorn application once again.
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.