were able to cool down to -45°C under ambient
As usual, every image coming down from the camera must be calibrated. I do that in MaximDL by using flat field images made with Gerd Neumann's "Aurora flatfield panel", since it is also suitable for OSC CCD sensors. Flat fields remove artifacts caused by inhomogeneities of the CCD sensor, dust particles on both the sensor and the optics, and vignetting. A master flat field should be calibrated by subtracting a master Bias frame.
Process your QHY8L images strictly in the following way in MaximDL:
- image acquisition with this OSC camera => RGBRAW
- image calibration RGBRAW => RGBCAL (using dark, bias, flat frames)
- color conversion (RGBCAL => RGB)
- color split (RGB => R,G,B)
- remove gradient (i.e. the light pollution) in R channel => Rclean
- remove gradient in G channel => Gclean
- remove gradient in B channel => Bclean
- color combine (Rclean,Gclean,Bclean => RGBclean)
- repeat from step (2) for all your images
- align all images
- stack all images
- further steps
Download an example here. Do NOT align your images before the color conversion, since this will move the RGGB map and you will loose the color information. The according procedure is also explained here.