I shot the Owl Nebula (M97) a few months ago, and barely had the Surfboard galaxy (M108) in frame. Since I shot it in narrowband, I decided to combine it with some old data I shot back back in 2021 as there's very little narrowband signal in the galaxy. So while M108 and the stars are true color, M98 in this pic is technically false color (although kinda close if you compare it to the 2021 pic. I think this does a great job of showing how much my processing has improved in the last 2 years, as the datasets for the galaxy and stars are identical. There's also a number of faint background galaxies in the pic.

Narrowband images were shot from a bortle Bortle 9 zone in July 2023, and the boradband was from Bortle 6 in March 2021.

Places where I host my other images:

Flickr | Instagram

Equipment:

• TPO 6" F/4 Imaging Newtonian

• Orion Sirius EQ-G

• ZWO ASI1600MM-Pro

• Skywatcher Quattro Coma Corrector

• ZWO EFW 8x1.25"/31mm

• Astronomik LRGB+CLS Filters- 31mm

• Astrodon 31mm Ha 5nm, Oiii 3nm, Sii 5nm

• Agena 50mm Deluxe Straight-Through Guide Scope

• ZWO ASI-290mc for guiding

• Moonlite Autofocuser

Acquisition: 15 hours 38 minutes (Camera at -15°C, unity gain)

• Ha - 43x360

• L - 91x120"

• R - 29x120"

• G - 29x120"

• B - 29x120"

• Darks- 30

• Flats- 30 per filter

Capture Software:

• Captured using N.I.N.A. and PHD2 for guiding and dithering.

PixInsight Preprocessing:

• BatchPreProcessing

• StarAlignment

• Blink

• ImageIntegration per channel per panel

• DrizzleIntegration (2x, Var β=1.5)

• StarAlign to new Ha and Oiii stacks

• Dynamic Crop

• DynamicBackgroundExtraction 2x

Luminance Linear:

• BlurXterminator

• NoiseXterminator

• ArcsinhStretch + HistogramTransformation to stretch to nonlinear

Narrowband:

• ArcsinhStretch + HistogramTransformation to stretch to nonlinear

• PixelMath to combine Ha and Oiii images into bicolor pic (used /u/DreamsPlease's formula)

R = iif(Ha > .15, Ha, (Ha*.8)+(Oiii*.2))

G = iif(Ha > 0.5, 1-(1-Oiii)*(1-(Ha-0.5)), Oiii *(Ha+0.5))

B = iif(Oiii > .1, Oiii, (Ha*.3)+(Oiii*.2))

• StarXterminator to completely remove stars

• BackgroundNeutralization

• Small stretches with HT

• NoiseXterminator

• Curve adjustments

RGB Linear:

• SpectrophotometricColorCalibration

• Slight SCNR Green

• HSV repair

• ArcsinhStretch + HistogramTransformation to stretch to nonlinear

• LRGBCombination with stretched luminance as L

• Various curve adjustments for lightness, contrast, hue, saturation, etc (with varying lum/star masks)

• PixelMath to add narrowband (this really only affected/overlaid the Owl nebula on top, not touching the stars, galaxy, or background)

Max(RGB , Bicolor)

• NoiseXterminator

• More curves

• invert > SCNR > invert to remove magentas from the background

• LocalHistogramEqualization (2 round of this at kernel 16 and 74 to affect different sized structures)

• MLT/SCNR for chrominance noise reduction in the galaxy

• DarkStructureEnhance

• BlurXterminator for star sharpening

• ColorSaturation

• final curves

• Resample to 70%

• FastRotation

• Annotation