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Image of the day 07/29/2019

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    Sh2-155 Cave Nebula( Caldewell 9 ) HaLRGB, 





    
        

            Sunil Bhaskar
    Sh2-155 Cave Nebula( Caldewell 9 ) HaLRGB

    Sh2-155 Cave Nebula( Caldewell 9 ) HaLRGB

    Technical card

    Resolution: 6428x7230

    Dates:Aug. 11, 2018Aug. 12, 2018Aug. 13, 2018

    Frames:
    Astrodon 3nm Ha 31mm: 100x200" (gain: 200.00) -20C bin 1x1
    Astrodon Gen II Blue 31mm: 50x180" (gain: 76.00) -20C bin 1x1
    Astrodon Gen II Green 31mm: 50x180" (gain: 76.00) -20C bin 1x1
    Astrodon Gen II Luminance 31mm: 100x120" (gain: 76.00) -20C bin 1x1
    Astrodon Gen II Red 31mm: 65x180" (gain: 76.00) -20C bin 1x1

    Integration: 17.1 hours

    Darks: ~20

    Flats: ~10

    Flat darks: ~10

    Bias: ~150

    Avg. Moon age: 1.26 days

    Avg. Moon phase: 2.74%

    Bortle Dark-Sky Scale: 1.00

    Astrometry.net job: 2808878

    RA center: 344.195 degrees

    DEC center: 62.437 degrees

    Pixel scale: 0.527 arcsec/pixel

    Orientation: 1.378 degrees

    Field radius: 0.708 degrees

    Data source: Traveller

    Description

    The Cave is a beautiful emission nebula displaying a resplendent star nursery along with the complementary reflection nebula which makes the interstellar gas look more pronounced, not to mention the dust lanes which are new star havens. This was taken from the Big Bend National Park where the skies are some of the best I have ever seen in my life.

    Processing details :
    Red, Green, and Blue :

    Full calibration with bias, flat, and dark frames
    Cosmetic Correction
    Weighting using Subframe Selector tool
    Registration
    Linear Fit to the weakest channel(this case Ha)
    ABE
    DBE
    Merging Ha to RGB :

    I tend to combine Ha data to RGB when everything is in the Linear state so the step involved are as follows :

    LRGB combination of R,G,B to get linear RGB image.
    NBRGBCombination script to merge Ha data to RGB and adjusting sliders to get the desired Ha potency :D
    P.S : No Processing is performed till this stage is over.

    HaRGB:

    Dynamic Crop
    Background Neutralization
    Color Calibration
    TGVDenoise and MMT noise reduction
    A curves stretch in Linear mode using a clipped RGB mask to bring out saturation details.
    Arcsinh stretch
    Histogram Transformation(Usually a couple of runs )
    Color Noise Reduction using ACDNR

    Luminance( :

    Full calibration with bias, flat, and dark frames
    Cosmetic Correction
    Weighting using Subframe Selector tool
    Registration
    Drizzle integration (2x)
    Automatic Background Extraction
    Dynamic Background Extraction
    Dynamic Crop(Matched to RGB)
    Deconvolution using a PSF created using DynamicPSF
    TGVDenoise and MMT noise reduction per Jon Rista's noise processing workflow
    Star rounding (Involving a Morphological Transform and a star mask )
    Masked Stretch
    A few iterations of Histogram Transformation.
    Curves to bring up the background level
    Medium scale noise reduction using MMT
    HDR Transform
    An ACDNR noise reduction to fix artifacts.
    Unsharpmask to bring out the features in the nebulosity.

    LRGB :
    LRGB Combination
    A strong MMT reduction to fix mottling issues followed by a detail enhancement MLT with a mask.
    Unsharpening if needed.
    SCNR green
    Curves Adjustment for aimed at boosting contrast/nebulosity without affecting stars using a combination mask.
    Resize and convert to jpeg

    Comments

    Author

    cyclops12321
    Sunil Bhaskar
    Like

    Sky plot

    Sky plot

    Histogram

    Sh2-155 Cave Nebula( Caldewell 9 ) HaLRGB, 





    
        

            Sunil Bhaskar