Calibration frames.

denababy

Hi, the clouds have been around for a while so I decided to build a calibration library, I have looked and looked, probably in the wrong places, anyway, do I have to produce the flats with the same exposure length as my lights in every case, I.e lights at 180seconds, do the flats need to match this. I know gain Etc. has to be the same. Can anyone advise please

wvreeven

Flats typically should be in the 1 to 10 second range, depending on the brightness of the source and the filter used. Try not to take shorter flats because that may lead to unevenly illuminated flats. But longer certainly isn't necessary.

Flats may be of any gain or temperature, as long as you have darks (and/or bias frames) of the same gain and temperature. If the darks match the exposure time of the flats they are commonly referred to as dark flats or flat darks (depending who you talk to) and then you will not need bias frames to scale the dark flats to the exposure time of the flats.