this post was submitted on 02 Nov 2024
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Nebula near LBN 325 [OC] (live.staticflickr.com)
submitted 3 weeks ago by lefty7283 to c/pics
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[–] lefty7283 5 points 3 weeks ago

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

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