M44 - Beehive Cluster / Praesepe (2022.01.07)

Lens aperture: f/5.6
Darks: 30s x 30 @ ISO 800
Offsets/Bias: 1/4000s x 30 @ ISO 800

Technical imaging session of the open star cluster M44. The goal was to test how Astroberry on a Raspberry Pi 4 works paired with an OnStep controller, and to check the performance of the EQ5 mount after modifications.

This was also my first attempt to use Brightness Masks in Photoshop to adjust star saturation separately from the background saturation. When I tried increasing saturation without masking the background—applying the adjustment to the entire layer at once—the red tint in the background became very noticeable. In this image, star saturation was increased by +30, while the background saturation was decreased by -100 and lightness increased by +7 to make it less black and slightly gray.

As a result, I like the background much more than in my previous photos, though it’s still not quite right—I need to find a way to make it smoother or more blurred, but my Photoshop skills aren’t there yet. The stars also don’t look very “colorful,” and further saturation adjustments don’t improve them (the colors start to look odd). I think I need better white balance next time, possibly based on some form of photometry, or I may reprocess this shot later with adjusted white balance.

In any case, the mount with Astroberry@RaspberryPi4 + OnStep is up and running and ready to be deployed at the Mayaky Observatory Station, so now I’m just waiting for suitable weather conditions :-)