Decided to just shoot a semi-random part of Cygnus. The large extended Ha region in Cygnus is unofficially called Smaug, and this is a photo specifically of the area around LBN 325/326. The nebulosity in this pic is false color, but the stars are true color RGB. I really love how this turned out with the narrowband palette, especially with the Oiii region on the right side looking almost like a true color Ha region. Captured over a shitload of nights from Aug-Oct 2024 from a bortle 9 zone.

Places where I host my other images:

Flickr | Instagram

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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: 57 hours 40 minutes (Camera at -15°C), NB exposures at unity gain and BB at half unity

• Ha - 111x600"

• Oiii - 127x600"

• Sii - 94x600"

• R - 48x60"

• G - 48x60"

• B - 44x60"

• 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

• DrizzleIntegration (2x, Var β=1.5)

• Dynamic Crop

• DynamicBackgroundExtraction

duplicated each image and removed stars via StarXterminator. Ran DBE with a shitload of points to generate background model. model subtracted from original pic using the following PixelMath (math courtesy of /u/jimmythechicken1)

$T * med(model) / model

Narrowband Linear:

• Blur and NoiseXTerminator

• StarXterminator to completely remove stars (to be later replaced by the RGB ones)

• HistogramTransformation to stretch nonlinear

RGB Linear:

• ChannelCombination to combine monochrome R G and B frame into color image

• SpectroPhotometricColorCalibration

• BlurXTerminator for star sharpening (correct only)

• HSV Repair

• StarXterminator to generate a stars-only image

• ArcsinhStretch + HT to stretch nonlinear (to be combined with starless narrowband image later)

• Invert > SCNR > invert to remove magentas

• Curves to saturate the stars a bit more

Nonlinear:

• PixelMath to combine monochrome Ha Oiii and Sii images into a color image with Jimmy’s Royale Palette

R = 0.3*Oiii+0.7*(Oiii^~(0.7*Ha+0.3*Sii))^1.2

G = ((Oiii*Ha)^~(Oiii*Ha))*Ha + _((Oiii*Ha)^(Oiii*Ha))*Sii

B = 0.9*Sii+Ha-Oii

• NoiseX again

• Shitloads of Curve Transformations to adjust lightness, hues, contrast, saturation, etc

• more curves

• Extract L --> LRGBCombination for chrominance noise reduction

• even more curves

• Pixelmath to add in the stretched RGB stars only image from earlier

This basically re-linearizes the two images, adds them together, and then stretches them back to before. More info on it here)

mtf(.005,

mtf(.995,Stars)+

mtf(.995,Starless))

• Couple final curves

• Resample to 60%

• Annotation