The good, the bad, and the M42 (again)

 

This is another attempt at M42, the Great Nebula in Orion (and friends).

There were a few changes this time, some good and some bad. First, I think my polar alignment was better (good). Second, I got a Bhatinov mask to help with fine focus (good). Third, I decided to try imaging without the light pollution filter, which ended up being bad. Despite an overall much longer integration time, there's a noticable drop in contrast for the dimmer parts of the nebula.

I also added flat frames to this one, but they didn't really seem to help with the vignetting - I might need to look into how I'm taking those to see what my problem is.

All exposures at 6400iso, 400mm FL, f7.1
Lights: 394 @ 30s, 91 @ 15s
Flats: 81
Darks: None (very cold out)
Bias: 87

Initial processing was done in Siril, separately for the 15 and 30 second stacks. Each resulting stack was processed globally in Darktable for color and contrast. Final processing and exposure combination was done in Gimp.