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Fixing blue star bloat
I have what is a common problem with many refractors: the red and green channels can be focused sharply, but some of the stars under the blue channel are significantly larger. I think what is happening is that even within the blue filter passband there is still significant dispersion, i.e. the color blue-green focuses ok, but the color blue-violet becomes out of focus. When viewing the blue image UNSTRETCHED, most of the stars are ok, and maybe only a little wider, but when viewing STRETCHED there is a significant blooming of some of the brighter stars. So then when I combine the images, the stars have a blue ring around them.
Anyway, is there a way to fix this in the program? I tried the checkbox of align stars, but that didn't help.
No indeed, halos are tricky. The light pollution correction may work a bit for very large halo's, but I think only when it's more of a gradient coming from just outside the frame for example.
I'm not talking about giant halos - it's just a few pixels worth.
Yes, so my example was for these more giant ones. There it would still work, for smaller ones there is no real solution yet.