[avandonk]

Do yourselves all a favour and dither your images. It is pointless stacking hot pixels on hot pixels or the 'holes' these pixels leave after over dark correction due to mismatched temperatures of darks and lights. In fact with dithering it is hard to see the difference between dark corrected image stacks and uncorrected dark image stacks.

This also has the effect of any sporadic erroneous pixels being totally eliminated. Cosmic rays come to mind.

Noise control starts with very good darks and flats. I routinely make flats from forty frames with forty darks for the flats. This eliminates the 'bias' problem. This can lead to banding for really faint stuff when stretched.

If you are scaling darks a stack of forty bias frames is also needed for proper scaling of the dark. Noise is an almost linear function with exposure and temperature so mathematically it is not difficult to deal with. The DC level of bias can throw this out. This has to be subtracted before any scaling of darks can be contemplated. Software like ImagesPlus do this automatically.

The reason for so many darks and flats and bias frames is that you want to minimise the statistical (Poisson) errors or noise that then are used to modulate your light frames to at least the statistical errors of your light frames. It is almost useless to correct for flats or darks with less frames than the number of frames of your lights IE DATA. This can corrupt perfectly good data by 'correcting' with noisy darks and flats.

As far as the darks I have total control over temperature so darks match lights. I also make master darks from forty darks.

If this is not possible then dithering really helps.

Bert