For some odd reason, I plan to take a lot of full disk images Monday after next. I'm having some issues getting with even brightness across the disk though. (Lunt 50, ASI120mm camera. I think the brightness issues are probably due to some sag in the focuser which could be fixed with $$$ in the future, but not in time) Here's a simple surface image before any attempts to correct this
I've tried creating a pseudoflat for this by taking the initial image and running a Gaussian blur on it. I've constrained the blur to the disk area since otherwise you get ugly edge effects. This looks good at first
But it still has some edge effects- note the brightening on the upper right. This ends up looking quite ugly when merged into a prom image- you get a black ring that doesn't look natural at all. I've tried fiddling with the size of the blurred image, making it very slightly larger and smaller to see if I can find a point where the pseudoflat won't do that, but I'm not having any luck. Anyone here with a lot more experience know a trick that can work? (Sorry for the size, but it's hard to see on the shrunken versions) Thanks in advance for any help.