Author Topic: No match for wide field images?  (Read 490 times)

RogueSquadron

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No match for wide field images?
« on: July 03, 2018, 05:38:57 AM »
Hello,

I took some constellation images yesterday with my DSLR and an 17mm lens on it. Stacking, aligning and calibration with bias and dark frames worked pretty well, debayering also.

But Observatory is not able to match the image. I have no WCS data in the image as the mount was not connected to the Mac by this time.

In general matching works. Observatory was able to match an image taken of Alioth (eps UMa), UCAC4 is downloaded and installed.

Not sure, why the larger image does not get matched.

Any hints? I attached the not matched image.

Thanks in advance, Rogue

Sander Berents

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Re: No match for wide field images?
« Reply #1 on: July 03, 2018, 06:39:58 AM »
If matching doesn’t work when providing a fairly accurate estimate for the center and pixel scale, you have set the frame size to its minimum (25%), and increased the search radius, then it could be that the stars in this wide field image are so small that Observatory rejects them as hot pixels. You may want to try the blind plate solver with the option to upload the whole image.
Sander Berents
Code Obsession, LLC
http://codeobsession.com

RogueSquadron

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Re: No match for wide field images?
« Reply #2 on: July 03, 2018, 07:15:47 AM »
Thanks a lot. Blind Solving worked, even with uploading stars only.

For local matching it would actually be very helpful to have a measurement tool of how many pixels are in a certain distance between to points.

I was able to determine the arc-distance between 2 stars on the image with another astro-Software, but had to guess how many pixels that would be in the picture to get the pixel scale.

After matching that tool could also be used for measuring arc distances.

Sander Berents

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Re: No match for wide field images?
« Reply #3 on: July 03, 2018, 07:49:38 AM »
Observatory has such tool. See the last one in the Measurement Inspector (Astrometry).

If an image is not plate solved it will display the separation in pixels and planar angle between two points.

If plate solved, it will also display the RA/Dec of the points, angular separation and position angle.
Sander Berents
Code Obsession, LLC
http://codeobsession.com

RogueSquadron

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Re: No match for wide field images?
« Reply #4 on: July 03, 2018, 07:54:19 AM »
Thank you Sander, just found the Asometry Section in the Measurement inspector.

Very impressive!