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I find with flats there is a little bit of art to it. Sometimes I find a flat can slightly overcorrect vignetting, other times not enough. Sometimes calibration leaves the lines in the ccd other times not.
So I don't think a rote approach is the way to go. You need to test what you have for its results when calibrating otherwise you're going to get some misses.
After doing the tutorial with Rick about PI it seems PI has the best calibration routine. CCDstack is quite good as well but is very memory intensive. Occassionally it will fail to align images. It does not like colour images. It does not tell you how many subs you just opened - they are not numbered, so you have to manually count them every time to keep track of total exposure.
Also I find its better to reduce vignetting physically and keep filters and ccd window clean rather than rely on flats to clean up your dust donuts and vignetting.
Depending on your camera and the type of shutter it has you can't do exposures of less than about 3 seconds with leaf shutters. If its a KAI chip then you can take flats without a shutter if the camera allows it like the SX cameras. SBIG have an even illumination shutter which is a good thing. But for leaf shutters which perhaps have other advantages (perhaps more light proof) they require 3 second minimum exposures otherwise you get shutter artifacts in the image that wreck the flat.
Temperature of the ccd should be the same as the lights when doing flats. That can make it hard to take a flat during the day.
Greg.
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