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Unless the hot spot/bright centre of your lights is really bad you can flat field them. I've done this with a few scopes with correctors namely Tak BRC250 and CDK 17.
It does put pressure on your flats, darks and biases being high quality. A bit off and you'll get poor results.
What worked for me was dusk flats or flats taken with roof closed and a white cloth cover on the tube. I expose to about 22 to 26,000 ADU with a 16803 camera. Camera in focus and same orientations as used for imaging.
Take quite a few. Then mean combine in CCDstack no bias subtract.
I make a good quality bias, same temperature as lights and quite a few.
Min/Max combine. I subtract the bias when I apply the flats and darks and use the bias for both flats and darks (so the darks can be scaled).
A high quality dark, again quite a few and min/max combine.
Doing the above worked very nicely.
For some strange reason subtracting the bias whilst making the master flat gave poor results and odd corrections. I don't know why. Greg.
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