Processing result of the Iris Nebula NGC 7023 LRGB data from the Big Amateur Telescope (B.A.T.)

LRGB data contributed to this image by the following B.A.T. Discord members ...

@Philipp Weber (Dr. Karl Remeis Observatory Bamberg, Germany):
CDK 20 @ f/6.8 + SBIG STX-16803
R: 2.75 h, G: 3.3 h, B: 2.95 h

@joelkuiper (Bortle class 1 sky):
Orion Optics CT12L @ f/5 + ZWO ASI 1600 MM Pro
L: 4.8 h, R: 7.6 h, G: 7.5 h, B: 7.4 h

@Ryan (Bortle class 8 sky):
William Optics FLT 132 + ZWO ASI294MM-Pro
L: 11 h, R: 1.6 h, G: 7.2 h, B: 2.8 h

@Steve (Bortle class 5 sky):
William Optics FLT 132 Triplet APO @ f/5.6 + Atik 460ex mono CCD
L: 4.8 h, R: 2.6 h, G: 3.3, B: 3.4

@MrCrazyPhysicist (myself, Bortle class 4 sky):
C 14 Edge HD + Hyperstar V2 + ZWO ASI 183 MM Pro
L: 2.1 h, R: 17 min, G: 22 min, B: 21 min

The Big Amateur Telescope (B.A.T.), initiated by Astrobiscuit, is a collaboration of amateur astronomers, who share their data in order to create deep, high-resolution images of Deep Sky objects and time-lapse animations of variable nebulae.

If you want to contribute data for this or other targets to the B.A.T. or help processing data, follow this link to the B.A.T. Discord server:

https://discord.gg/WK8qmrqcpq

Remaining issues: The color saturation is quite excessive. Not sure if there are indeed faint emission nebula at the edge of the blue reflection nebula. There are some hot pixels in the image which I should correct during the next revision.

Large parts of the new workflow are based on the PixInsight Fundamental Videos for NGC 3486 (2021 version) by Adam Block

Post-Processing:

PixInsight

LRGB channel
star alignment, NSG script, image Integration with Min/Max rejection algorithm (clip high pixels off), dynamic crop, dynamic background extraction

RGB processing part 1
linear fit of R & G channels wrt B channel, RGB channel combination, Autocolor script, SCNR (minimum neutral, amount = 0.4), EZ Soft Stretch

L processing part 1
Arithmetic average of L data and luminance data from RGB image.

L processing part 2 (histogram stretch)
L_masked = masked stretch, L_manual = manual histogram stretch

arithmetic average of both stretches with PixelMath:
L_enhanced = .5 * (L_masked + L_manual)

HDRMT: Number of layers = 7, Scaling function: Gaussian (5), Lightness Mask, Deringing

LRGB processing
LRGB combination with chrominance noise reduction, color saturation enhancement using curves transformations, remove green tint with histogram transformations

LRGB_MMT = MMT with Bias = 0.1 on layer 4

remove stars with StarNet2, create luminance mask, apply luminance mask, increase color saturation of nebula, remove luminance mask, create range mask, invert range mask, enhance faint dust features with curves transformations, remove range mask, LocalHistogramEqualization Kernel Radius = 120, Contrast Limit = 1.5

Sharpening of L
enhanced luminance sharpening using this video by VisibleDark based on this tutorial on chaoticnebula.com

Denoising with Topaz 6 (non-AI version)
Overall Strength = 0.07

Finally, add stars to starless image using Pixelmath, final contrast/color saturation enhancements with curves transformations and color corrections with histogram transformations.

Adobe Lightroom 6.14
Some final color and contrast tweaks