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  • M17 is also known as The Swan Nebula (the bright core is swan shaped, esp when viewed visually through a telescope). Also pictured it the M18 star cluster off to the right.

    I originally shot this back in 2019 and decided to reprocess it since we have fun new tools and techniques (and I kinda know what I'm doing now with narrowband processing). I decided to keep the palettes similar overall, but with a less agressive stretch and more 'natural' look to the nebula. The noise reduction is a lot better when comparing the images at 1:1 (long gone are the days of TGV/MMT noise reduction!). Captured over 2 nights at the in May, 2019 from a Bortle 7 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
    • Agena 50mm Deluxe Straight-Through Guide Scope
    • ZWO ASI-120MC for guiding
    • Moonlite Autofocuser

    Acquisition: 8 hours 10 minutes (Camera at Unity Gain, -15°C)

    • Ha- 42x300"
    • Oiii- 56x300”
    • Darks- 30
    • Flats- 30 per filter

    Capture Software:

    • EQMod mount control. Captured using N.I.N.A. and PHD2 for guiding and dithering.

    PixInsight Processing:

    • BatchPreProcessing
    • Blink
    • ImageIntegration
    • DrizzleIntegration (2X, VarK 1.5)
    • DynamicCrop
    • 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:

    • BlurXTerminator
    • NoiseXTerminator
    • STF Applied via HT to stretch nonlinear

    Nonlinear:

    • PixelMath to combine monochrone Ha and Oiii channels into color image (using ForaxX's bicolor palette):

    R = Ha

    G= ((OiiiHa)(Oiii\*Ha))\*Ha + \((OiiiHa)~(OiiiHa))Oiii

    B = Oiii

    • SCNR Green
    • LRGBCombination with stretched Ha as luminance
    • Shitloads of curve transformations to adjust lightness, contrast, hues, saturation, etc
    • LocalHistoGramEqualization 2x - one at scale 16 for fine details and one at 512 for large structures
    • More curves
    • DarkStructureEnhance
    • MLT for small scale chrominance noise reduction
    • NoiseXTerminator
    • Even more curves, some masked to just the core of the nebula
    • Resample to 60%
    • Annotation