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Astrophotography @lemmy.world
lefty7283 @lemmy.world
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The Flying Bat and Squid Nebulae

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  • This target has always been a goal of mine since starting in this hobby. While the Flying Nebula (aka Sh2-129, all the red stuff), the Squid Nebula (aka OU4, the blue stuff) was only discovered in 2011. It's stupidly faint. Because of this, and my horrible light pollution, I had to get a ton of exposure time to bring it out, and ended up getting 110 hours total time on it. This is a combination of images taken through hydrogen-alpha and oxygen-iii filters for the nebulosity, plus RGB filters for true-color stars (the nebulosity is kinda close to true color). I have no clue why the Ha region is called 'the flying bat', but the Oiii structure sure looks like a squid alright.

    Captured over a shitload of nights from September to December, 2023. Broadband data 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: 110 hours 15 minutes (Camera at -15°C)

    BB exposures at half unity gain (76/15), Ha at unity gain (139/21)

    • Ha - 212x600"

    • Oiii - 428

    • L - 200x120"

    • R - 69x60" 69 71 66

    • G - 71x60"

    • B - 66x60"

    • 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:

    • Honestly just StarXterminator and EZ soft stretch to bring them nonlinear.

    • Duplicated the Oiii before stretching to be used for advanced narrowband combination:

    Oiii advaned narrowband combination:

    These steps largely follow the ones in Jimmy/NightPhoton's advanced narrowband combination guide.

    • Combine Oiii with Green broadband channel channel (OGG palette)

    • BackgroundNeutralization

    • ColorCalibration

    • StarXterminator to completely remove stars

    • PixelMath to subtract green continuum spectrum, leaving just Oiii signal

    • HistogramTransformation to stretch nonlinear

    • NoiseXterminator + a little concolution

    • CurvesTransformation to adjust black point/contrast

    • Clone stamp to remove a couple background artifacts

    • image saved as 'NB', to be combined later on in nonlinear processing

    RGB Linear:

    this is really just to have natural star colors

    • SpectroPhotometricColorCalibration

    • BlurXTerminator

    Really loving the star correction with its new AI v4 update

    • HSV Repair

    • StarXterminator to make a stars-only image

    • ArcsinhStretch + Histogram transformation to bring stars nonlinear

    Nonlinear processing:

    • Combined stretched Ha and Oiii images into a color image using ForaxX's HOO palette:

    R = Ha

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

    Oiii

    • Background Neutralization

    • Shitloads of Curve Transformation to adjust lightness, saturation, contrast, hues, etc with various masks

    • LocalHistogramEqualization

    • Added in NB image from earlier per the advanced narrowband guide

      only difference from the pixelmath in the guide is that I added NB to the green and blue channels (0.6 and 0.9, respectively) instead of red

    • HistogramTransformation to adjust the black point

    • More curves

    • MLT for medium scale noise reduction in the squid

    • ColorSaturation to slightly desaturate the red nebulas

    • NoiseXterminator

    • Even more curves

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

    This basically re-linearizes the two images, adds them together, and then stretches them back to before

    (Jimmy is a processing wizard when it comes to writing up this independent starless processing stuff)

    mtf(.005,

    mtf(.995,Stars)+

    mtf(.995,Starless))

    • Guess what more curves

    • Another round of NoiseXterminator

    • MLT for some small scale chrominance noise reduction

    • Few more slight ColorSaturation adjustments

    • Resample to 60%

    • Annotation

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