To those maybe one or two of you keeping track of the Saga of Stu's Astrophotography, I recently figured out how to connect my camera to my school's 3" and 5" refractor finder scopes so as to capture larger fields of view (my camera on the school's 16"/18" Cassegrain results in a field just shy of 15x10 arcmin). See http://www.bautforum.com/showthread.php?t=37857 for more on this.
So Saturday I finally got to the 'scope when it was a clear night (albeit a 99% full moon). I discovered I couldn't hook up to the 5" because it's a 2" barrel and there was no eyepice projection equipment for that size. I discovered that I could not use my camera at prime on these 'scopes. I finally was able to get hooked up to the 3" refractor, and I went on a "Mini-Messier Marathon" (say that 3x fast) taking 120-sec shots of various M## objects (a post with the spoils of them is forthcoming).
However, I discovered this weekend while I was processing some of them that the chromatic aberration off to the sides is somethin' fierce. In the center ~25% of the view, the stars are nice white/blue/red/yellow balls on the order of 10 arcsec across for my focus/seeing, which is as good as I've ever gotten from Boulder. But closer to the edges, the stars make some lovely rainbows with red radiating inward and purple radiating outward, with the other colors inbetween.
So to get to the point of this post ... does anyone know how to take care of this in an "easy" way, either at the 'scope, or in processing in PhotoShop?
I've come up with two "solutions" and I don't like either of them: The first is to take several images of an extended object, moving the 'scope a little for each shot, and then stitching together the centers of each fram where the aberration isn't detectable. The second way would be to edit each color channel in PhotoShop separately, doing a scale transform on the red, increasing its size to around 100.5% and then doing the same with the blue, decreasing its size to around 99.5% (or whatever it takes to line them up).
Anyone encountered this before and have a better solution?