Leo Triplet

Acquisition:

Bortle 7 skies
Nikon D5600 camera (unmodified)
ISO 200
Astro-Tech AT102ED refractor, 714mm focal length, f/7
HoTech 2" SCA field flattener (1X)
iOptron CEM26 mount
30s x 363 frames (3h)

Processing:

Siril 1.2.1:

Crop to 4400x3300px
BQ Octantis' technique of white balance, background subtraction, and histogram conditioning
StarNet:
- star desaturation
- background: SCNR, GHT stretch, background extraction, saturation
- stars: synthetic blue (B=2*G-R), modified arcsinh stretch, saturation

RawTherapee 5.9:

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

GIMP 2.10:

Luminance curve
Saturation
Levels (midpoint adjustment only)