• @lefty7283OPMEnglish
    5•7 days ago

    So technically 32 Cygni is just the bright star in the pic, and the rest of it is just hydrogen gas floating around in space. The constellation Cygnus has a ton of this hydrogen-alpha gas floating around, and I kinda just pointed at a semi-random spot in the constellation to get a pic. Although this was taken with an Ha filter, the stars are true color RGB, and I mapped the Ha channel to red so it closely resembles the actual color of hydrogen-alpha. Also for those curious here is a starless version that better shows the faint nebulosity/structures. Also pls ignore the crunchiness around 32 Cyg itself, it’s an artifact of my camera’s microlensing + the star removal program I use. Captured over like a dozen nights in December 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: 29 hours 18 minutes (Camera at -15°C), unity gain

    • Ha - 161x600"

    • R - 51x60"

    • G - 59x60"

    • B - 48x60"

    • 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 from each the image

    • HistogramTransformation to stretch nonlinear (calling this the Ha image now)

    Broadband/RGB linear:

    • ChannelCombination to make color image from R G and B stacks

    • StarX (correct only)

    • SpectrophotometricColorCalibration

    (duplicated image at this point, to be used for stars only processing later)

    • StarX to completely remove stars (at this point it’s just background, with a little bit of signal in the R channel)

    • Blended unstretched Ha image into the red (and a little bit of the blue channel) with this pixelmath:

      R = $T+B*(Ha- med(Ha))

      G = $T

      B = $T+B*0.2*(Ha- med(Ha))

      honestly can’t remember what I used for the B constant, but the default is 2 in my pixelmath ¯\_(ツ)_/¯

    • HistogramTransformation to stretch nonlinear (calling this the Starless image now)

    Stars only processing:

    • HSV repair to fix blown out star cores

    • StarXterminator to generate an image containing only the stars (without any background)

    • ArcsinhStretch + Histogramtransformation to stretch nonlinear (Calling this the Stars image now)

    Nonlinear:

    • LRGBCombination to add the stretched Ha image to the stretched Starless image as a luminance layer

    • NoiseXterminator

    • Background neutralization

    • Several curve transformations to adjust lightness, contrast, saturation, color balance, etc

    • LocalHistogramEqualization

    • Another round of noiseX

    • Pixelmath to add in the stretched RGB Stars 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))

    • few more curve adjustments

    • FastRotation 180 degrees (pic was originally upside down)

    • DynamicCrop again (just a little bit)

    • Resample to 60%

    • Annotation

  • @GnomieEnglish
    3•6 days ago

    That’s a terrific image but even better for me, a beginner astrophotographer, is all the details in the processing. Thank you for going to the effort to include that.