Very challenging image set - faint comet, bright stars, near horizon, twilight starting

(If you want this image set for test/evaluation purposes, I'm happy to provide.)

Comet 22P Kopf in the morning sky as twilight starts.

Sony a6300, 200mm, f/2.8, 20-second exposures, ISO 6400, stack of 77 frames.

First screen grab is a very tight crop on the final stack. The comet (approx mag 12) is the small, slightly smeared green smudge in the center.

I did not even attempt to align/register on the comet because...

Second screen grab is a single calibrated image. The comet might be visible as a slight increase in sky background, but it's bracketed by two brighter stars. I don't think any automated routine will centroid on the comet, so I just aligned on the stars. (I wish I had some sort of manual comet stacking capability where I tell APP the drift rate of the comet in pixels per minute of time, and rely on the time stamp of the individual files.)

Third image is a wider view. Comet is just left of center. Note how uneven the sky background is. Down low there is more skyglow/natural sky brightness, and light pollution, and the glare from above is because Venus is just above the edge of the frame.

Fourth screen grab shows what Astro Pixel Processor can do to flatten out the sky background. Pretty good, but I don't know why the color saturation has also been pulled to near zero. (I was also testing the 'calibrate star color' routine because the stars have an overall slight green tint after normalizing to create a neutral background.)

This is a challenging set of data on which to properly stack a comet, to get color 'correct', and deal with the light gradients from natural and man made light sources. I'm not even close to getting these things corrected.

Fifth image is the entire frame that the 200mm lens covers. The comet is almost impossible to spot a bit left and above center.

Last screen grab is from planetarium software. When I started the imaging run the comet was only about 6 degrees above the horizon. I kept taking images for 25 minutes until the sun was at about -16 degrees.

This imaging run was a test to see what results I can get with a comet that's close to the sun. The comet is low in the sky, and I have a short time to get images before twilight puts an end to it. I chose the 200mm lens because it's one stop faster than the 300mm.

Again, I'm happy to provide this image set if you think it will help test and improve APP's capabilities.