NGC 6820 and 6823 first attempt

[Padraic M]

Over the last few clear nights I've concentrated on NGC 6823 & NGC 6820. NGC 6820 (the dark pillar left of centre) is a small reflection nebula in Vulpecula, and NGC 6823 is an associated star cluster. They are both embedded in a faint emission nebula Sharpless 2-86. Over three nights I managed to get:

109x60s lum
44x60s red
38x60s green
45x60s blue

Total exposure just under 4 hours. The numbers are odd because I have guiding issues. The mount makes lurches in declination from time to time which ruin the current sub. 

This is after sorting out the following problems:

- focus was poor (now using electronic focusing, autofocus through APT)
- realising that I don't need to rotate the camera after a meridian flip - DSS can deal with it
- realising that flats are required for each filter used. The APT CCD Flats Tool is useful for capturing flats and dark flats. Not 100% sure that it's correct just yet.

DSS does a good job once you figure out the process. I stacked luminance first, and identified the best frame. Stacked each of RGB using the best luminance frame as the reference. Stacking mode of Standard used to make sure that all stacked frames are aligned with the lum reference.

Any tips on stretching and setting the colour balance in Gimp would be appreciated. I'd like to have more red in the final output above, and slightly less green in the background, but can't seem to get it right without adding magenta. Overall I think the colours should be more saturated, and I would have thought that with 4 hours exposure I would be able to bring out more detail in the nebulosity.

Stars are a bit fat, and prone to coloured halos.

Lots of learning happened with this image as it's by far my most ambitious shot so far. I'm starting to understand the importance of setting up a rig correctly, getting all necessary calibration frames, and leaving the rig alone until the target has been captured completely.

Equipment:

Mount: HEQ5 Pro. Needs a strip-down and lubrication (ala Astrobaby) and a belt mod.
Scope: Celestron C8 SCT w/0.6x focal reducer. Longer focal length than I'd like, but all available given lock-down.
Camera: ZWO ASI1600MM Pro cooled to -10c. Considering moving to -20c for the next project.
Guiding: Starwave 50mm & ZWO ASI290MM Mini
Software: Sharpcap polar alignment. APT, PHD2, Stellarium. Deep Sky Stacker. Gimp.