Quote:
Originally Posted by Octane
OICURMT,
...You don't need bias/offset frames as that information is already contained within the darks. The only time these are potentially of any benefit is when you're scaling dark frames (that is, you try and subtract a 10 minute master dark frame from a 5 minute light exposure). Not sure why you'd do this and not just take dark frames on the night, itself...
H
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Not quite sure about this and I'm no expert, but granted the dark frame has the bias error already in it, fine if you just subtract the darks. But if you use both darks and flats, as the flat
frame has the bias error in it as well, aren't you going to subtract out the bias error twice (or at least a proportion of it) which will in fact be adding noise, unless you subtract the bias from the flats. Not quite sure how the various programs out there use the bias frames.