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"Eyeshadows" on the stars ?

ZWO ASI585MC Pro Steffen Hirtle GraXpert Siril Team Siril Artifacts Help Needed
6 replies•298 views
Reiner A. Merz avatar
Reiner A. Merz avatar
Sometimes I get these eyeshadows on the stars (blue color spots). Can someone help me ?

24 x 180s with ZWO585MC Pro, APO125 with Korrektor 0,8 = 780mm
Stacked with siril
Denoised with GraXpert
Tuned with Gimp

Thanks ! Reiner
Ethan Sweet avatar
Ethan Sweet avatar
It's chromatic aberration.  Put simply, your telescope is focusing the different wavelengths of light at different points. Very common with camera lenses and cheaper telescopes.
Well Written Concise
Reiner A. Merz avatar
Reiner A. Merz avatar
Ths is an excerpt from a singleshot fits-file only RGB-converted and background extracted. You can see the "eyeshadow" .
I used a 2"CLS_Filter from sybony.
Is it caused by light-pollution ?
andrea tasselli avatar
andrea tasselli avatar
Your image seems slightly out of focus. Try tighting up the focus and see whether the blue disappers.
Tony Gondola avatar
Tony Gondola avatar
As others have mentioned it's looks like chromatic aberration from your optics. You can also get a color dispersion like this from shooting to low to the horizon. At anything much under 40 to 50 degrees elevation the atmosphere can ack like a prism separating the colors slightly vertically.

If you take a test shot near the zenith you can separate out the effects. If it's the optics then a "fringe killer" filter will help to minimize it.
Helpful Concise
Reiner A. Merz avatar
Reiner A. Merz avatar
Thank you very much for the answers and the advises.The telescop-seller guessed, that the telescope was not good in focus.
I will test the different suggestions and tell you the results and successes !
Reiner A. Merz avatar
Reiner A. Merz avatar
andrea tasselli:
Your image seems slightly out of focus. Try tighting up the focus and see whether the blue disappers.

I just read this answer ! i think I will pay attention to control the focs more often ! Thanks !