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  • 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 = 0.3Oiii+0.7(Oiii~(0.7Ha+0.3Sii))1.2

    G = ((OiiiHa)(OiiiHa))Ha + ~((OiiiHa)(OiiiHa))Sii

    B = 0.9Sii+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