Vignetting

So that is sometimes tricky indeed. What I did in the past (when I didn't have flats yet), was to first calibrate all my lights with darks and bias (bias being 0.02 seconds at the minimum) and save those lights (tab 2, first calibrate, then go down and select to save them). Then I would load 1 of those calibrated lights and use that to make an artifical flat. Then I load in the calibrated lights again and use that flat to correct.

I think the important step was to calibrate the lights first with darks or bias. Of course the best is always a real flat.