Messier 3 (and NGC 5263)

NGC 5263 is the faint galaxy off to the right. It's around 200 million light-years away.

Acquisition:

Bortle 7 skies
Nikon D5600 camera
ISO 400
Astro-Tech AT102ED refractor, 714mm focal length, f/7
HoTech 2" SCA field flattener (1X)
iOptron CEM26 mount
30s x 239 frames (1h 59.5m)

Processing:

Siril 1.2.1:

Crop to 4000 x 3000px
BQ Octantis' technique of white balance, background subtraction, and histogram conditioning
Star desaturation
Synthetic blue (B=2G-R)
Modified arcsinh stretch
Background extraction
Saturation

RawTherapee 5.9:

L*a*b* CL curve (to reduce chrominance noise)
Luminance noise reduction

GIMP 2.10:

Luminance curve
Saturation
Temperature reduction (a bit too orange)