Flats from ASI 1600 mm Pro don't work anymore

Here are some images for reference as well if helpful. Stretched them more aggressively to show the difference in the calibration

linear single frame, 30% stretch:

calibrated single frame, 30% stretch:

integrated:

Hi,

this looks like overcorrecting, I do not think your darks are at fault, this is usually an issue with your flats. I had a similar problem when I changed the USB speed value (although I cannot quite explain how that could affect things). Also, check offset and double check gain in the FITS header of your flats, darks, dark-flats (and, possibly, bias, which is not recommended to use). Posting a link to raw FITS frames would also help. You do not seem to have any dust motes in your images, so if new flats do not help or are not an option, you could try googling "synthetic flats" for a way to correct your lights for vignetting without flats. It has worked for me before with my ASI1600.

Thanks! I threw a sample of dark, flat and darkflat up and looking at their headers I noticed that just the dark has an offset value. I'm thinking that what happened was that SGP stopped supporting the existing driver that allowed offsets and now it defaults to something else (50 i believe). The newer frames don't have an offset value and I noticed the egain value was different. I will try recapturing the darks tonight and will repost if that solved the issue. Fingers crossed!

Just closing the loop for anybody searching for this in the future - that was definitely the issue. Finally getting calibrated images again, thanks for the help!

Excellent find! These can be hard to get at.