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Celestial hemisphere:  Northern  ·  Constellation: Cassiopeia (Cas)  ·  Contains:  IC 1590  ·  NGC 281  ·  Sh2-184
NGC 281 / IC 11 / Sh2-184 - Pacman Nebula, Jonathan W MacCollum
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NGC 281 / IC 11 / Sh2-184 - Pacman Nebula

Link: https://jonsastro.z13.web.core.windows.net/eigenVector.Pacman.html
NGC 281 / IC 11 / Sh2-184 - Pacman Nebula, Jonathan W MacCollum
Powered byPixInsight

NGC 281 / IC 11 / Sh2-184 - Pacman Nebula

Link: https://jonsastro.z13.web.core.windows.net/eigenVector.Pacman.html

Equipment

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Acquisition details

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Description


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The Pacman Nebula is a bright emission nebula in the constallation Cassiopeia.



Equipment:


    [li]
    Orion 8in F4.9 1000mm Newtonian Reflector


      [li]Flocked / Primary mirror replaced due to turned-down-edge[/li]


    [/li]

    [li]
    Skywatcher F4 Aplanatic Coma Corrector


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    Astrodon I Series 5nm Ha, 3nm Oiii, 5nm Sii narrowband filters


    [/li]

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    ASI183mm Pro cooled to -15C


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    Celestron CGEM Mount


      [li]
      Self tuned / hacks to get guiding stable include:


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        Intentional offset polar alignment so dec always pulses in one direction


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        Balance "west" heavy (rather than the recommended east) so that the ota "falls" onto the gear teeth rather than get "lifted"


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        Factor Reset hand-controller daily (to prevent cgem from being possessed and forgetting where the meridian is on subsequent night)


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        Dither in RA only


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      [/li]


    [/li]

    [li]
    Data Acquired using N.I.N.A and Guided with PHD2


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Acquisition Details (excluding rejected frames):


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    Ha: Best 36 of 40x10min (6 hours 00 minutes)


    [/li]

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    Oiii: Best 27 of 44x10min (4 hours 30 minutes)


    [/li]

    [li]
    Sii: Best 34 of 51x10min (5 hours 40 minutes)


    [/li]

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    Total: Bests 16 hours 10 minutes of 22 hours 30 minutes


    [/li]



The resulting image is a combination of the following steps:


    [li]
    Inspected all subs for bad images with Blink, discarding 40 subs due to clouds or otherwise poor guiding


    [/li]

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    Calibrated all subs with their corresponding master flat and master dark


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    Used subframe selector to weight Ha, Oiii, Sii separately for integrating each


    [/li]


(20*(1-(FWHM-FWHMMin)/(FWHMMax-FWHMMin))

+ 10*(1-(Eccentricity-EccentricityMin)/(EccentricityMax-EccentricityMin))

+ 30*(SNRWeight-SNRWeightMin)/(SNRWeightMax-SNRWeightMin)

+ 20*(Stars-StarsMin)/(StarsMax-StarsMin))

+ 30

    [li]
    Selected the best sub from subframe and blink to use as a reference frame which stacking each set


    [/li]

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    Created a SNR Optimized Synthetic Luminance by integrating the three resulting stacks documented by Juan Conejero of the PixInsight Development team.


    [/li]

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    Cropped the stacking edges of the integrated masters


    [/li]

    [li]
    Linear fit the Ha and Sii images to Oiii for the initinal color balance


    [/li]

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    Combined the Sii as Red, Ha as Green and Oiii as the Blue channel to create a color RGB image


    [/li]



Luminance Processing:


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    Dynamic Background Extraction


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      6 large points (Radius: 75 and 50)


      [/li]

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      Subtraction/Normalized


      [/li]


    [/li]

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    Automatic Background Extractor


      [li]Function degree 1 with normalization[/li]


    [/li]

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    Deconvolution was done on a separate copy of the luminance with


      [li]
      No deringing


      [/li]

      [li]
      wavelet regularization with 5 layers and strong but reducing amounts/thresholds


      [/li]

      [li]
      A starmask was created from a separate unmodified copy to replace the stars with the origional superluminance, eliminating the ringing artifacts from deconvolution as similarly documented by /u/OkeWoke


      [/li]


    [/li]

    [li]
    Noise Reduction was done using TGV Denoise with a low contrast mask and an autostretched local support and MMT with a very protective luminance mask


    [/li]

    [li]
    Combination of Histogram Transformation and Masked Stretch


    [/li]

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    Deconvolution with a star mask and Parametric PSF to tighten star cores


    [/li]

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    Morphological Transformation with a contours based star to shrink the overall intensity stars


    [/li]

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    Local Histogram Equalization - Two rounds at high scale with low amounts


    [/li]

    [li]
    S-Curve for overall contrast


    [/li]

    [li]
    HDR Multiscale Transformation - 6 Layers with a mask protecting the stars


    [/li]



SHO Processing:


    [li]
    Dynamic Background Extraction


      [li]19 large points using Subtraction/Normalized[/li]


    [/li]

    [li]
    RGB Workingspace set to 1,1,1


    [/li]

    [li]
    Remove Magenta from SHO Stars (Invert+SCNR Green+Invert)


    [/li]

    [li]
    Noise Reduction using TGV Denoise with a low contrast mask and an autostretched local support


    [/li]

    [li]
    Noise Reduction using MMT with a very protective luminance mask


    [/li]

    [li]
    Morphological Transformation with a contours based star to shrink the overall intensity stars


    [/li]

    [li]
    Histogram Transformation to stretch to non-linear


    [/li]

    [li]
    Channel Combination in CIE L*A*B mode to add the Synthetic Luminance to the SHO color image


    [/li]

    [li]
    Additional Star Shaping with Morphological Transformation with Star Masks and Contours based star masks


    [/li]

    [li]
    Additional sharpening and noise reduction using ATrousWaveletTransform


    [/li]

    [li]
    Dark Structure Enhance script to bring out dark gobules throughout the nebula


    [/li]

    [li]
    Various curves to bring the Ha background to Brown, Soften the Green Overcast, and enhance contrast


    [/li]

Comments

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NGC 281 / IC 11 / Sh2-184 - Pacman Nebula, Jonathan W MacCollum

In these public groups

ZWO ASI183/QHY183
/r/astrophotography
Narrowband imaging
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