Messier 92

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 279 frames (2h 19m)

Processing:

Siril 1.2.1:

Crop to 4000x3000px
BQ Octantis' technique of white balance, background subtraction, and histogram conditioning
Borodog's synthetic blue (B=2*G-R) (to reduce blue star bloating)
Modified arcsinh stretch
Generalized hyperbolic stretch
Background extraction
Saturation

RawTherapee 5.9:

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

GIMP 2.10:

Luminance curve (slight)
Saturation (slight)