By the way, you did a great job in noise reduction - I will have to visit your website again and take a deeper look into your NR techniques...
Yes, at the risk of removing true signal as well you can get rid of this artifact by the background modelization techniques. However, as you stated before (#115): "The thing that is curious to me is, the pattern seems to be quite consistent, and yet it is still not removed with dark calibration. I am having a hard time understanding why that is. If the pattern is so consistent that it shows up the same night after night, even days or weeks apart, why can it not be calibrated out?"
My primary concern:
1) Is it possible to take better calibration frames somehow?
2) is it possible to enhance the calibration process in some way?
3) is this remaining background artifact not removable by the calibration process at all?
I am curious about your judgement of the 150 s darks.
So, your 150s darks seem to work well. They produce a clean master, and I cannot really see the pattern in the master. The glows are fairly strong, though (and, I guess I wasn't aware, there are apparently two starbursts), so that makes it tough to evaluate anything else about the darks. I am currently calibrating each individual dark frame with the master, and I'll then integrate the calibrated darks to see what I get.
I did experiment a bit with some of the lights I calibrated with the master dark. I tried VNG, Bilinear, and SuperPixel. I noticed that with VNG and Bilinear, I could see a bit of pattern around the periphery, which is probably the beginnings of the issue being discussed in this thread. With SuperPixel, however, I could barely see the same pattern, and the color of the background was much more uniform.
So, I am curious, could you process your entire stack with SuperPixel, and integrate the result, and see what you get?
I was also interested in the color differences between VNG and Bilinear...very stark green cast with VNG, much more neutral color with Bilinar. Bilinear is not really the best way to demosaic, but the color differences were interesting.
I would like to try a bayer drizzle as well, and see what the outcome is.