I have been not using darks lately, other than to establish a bad pixel map (cosmetic correction in PI). I just wasn't sure there was any value in them other than finding those bad pixels. Between dithering and the cosmetic correction, I thought any remaining problems were down in the noise (so to speak).
In my latest image with IC 1340, the dragon head, I noticed a very faint band. I haven't noticed this before, probably because I haven't been using such narrow band filters. But it was clearly there. When I checked my bias frame, nothing was showing in that location. But when I checked a long exposure dark frame, sure enough, the band was there.
I decided when processing some additional data I gathered last night to try processing with and without a dark and see what happened. Sure enough, the dark removed the band. I'll be using them again, at least for this narrow band work.
First the image processed without a dark. Notice the very slight band just to the left of the left portion of the nebulosity.
In my latest image with IC 1340, the dragon head, I noticed a very faint band. I haven't noticed this before, probably because I haven't been using such narrow band filters. But it was clearly there. When I checked my bias frame, nothing was showing in that location. But when I checked a long exposure dark frame, sure enough, the band was there.
I decided when processing some additional data I gathered last night to try processing with and without a dark and see what happened. Sure enough, the dark removed the band. I'll be using them again, at least for this narrow band work.
First the image processed without a dark. Notice the very slight band just to the left of the left portion of the nebulosity.
Second, the Image using Darks in addition to the Bias and Flats used in processing the first image.