this post was submitted on 22 Sep 2023
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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:
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