thanks guys,
I read somewhere that if you divide one master flat by another master flat, the result should be a perfectly flat or something like that, whats this about? Is this what you mean by a "mostly featureless result" Rick. Is it to tell if your flats are good enough?
On a different note, when subtracting the master dark and dividing dark subtracted master flats from the light frames, is it performed on each light frame or a stack of light frames (luminance stack or red filter stack for example)
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thanks
Josh