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M78 Reflection Nebula in Orion

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#1 pbkoden

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Posted 19 January 2019 - 12:24 AM

I've been working on this image since mid November. Taken over 10 nights and totaling just over 50 hours of integration. The darkest I've measured my skies is 20.04 on my SQM-L meter, but some of the RGB data was captured with a partial moon up in significantly worse skies. All processing other than the watermark was done in Pixinsight.

 

I ran into a couple big challenges completing the image. 

 

One, over half of my integration time was plagued by really funny star shapes. I finally tracked it down to a secondary dew heater that was too hot (I posted about it in another topic). I didn't want to toss hours and hours of data, so the final image has the stars and brightest parts of the nebula pulled only from the last three nights of luminance data after I discovered and fixed the dew heater issue. The dimmer luminance areas and all of the RGB data have the full integration to get the noise as low as possible. This was done with a linear fit of the two integrations, range mask based on a stretched image, and copy over with pixelmath. I worked amazingly well.

 

Two, I had some really bad gradients to deal with (probably from the multiple nights and some moonlight). ABE was giving me artifacts and I didn't think DBE would work due to all of the background nebulosity, I resorted to using synthetic flats to tame the master L/R/G/B images. I think I finally got something workable, but my background data probably isn't as true as if this were taken from nice dark skies.

 

The luminance data after the full integration was clean enough were I probably didn't have to do any noise reduction. I did go ahead and run a light TGVDenoise per Jon Rista's workflow, but that's it.  

 

Capture details:

  • 186x240" Lum Astrodon
  • 168x300" Lum Astrodon
  • 102x300" Red Astrodon
  • 101x300" Green Astrodon
  • 98x300" Blue Astrodon

 

Here is my overall processing workflow:

 

Luminance:

  • Full calibration with bias, flat, and dark frames
  • Cosmetic Correction
  • Weighting using Subframe Selector tool
  • Registration
  • Drizzle integration (2x)
  • Background Extraction with a synthetic flat made using MMT, Clonestamp, and Convolution
  • Dynamic Crop
  • TGVDenoise per Jon Rista's noise processing workflow
  • Star size reduction using Morphological Transform
  • Histogram Transformation

Red, Green, and Blue:

  • Full calibration with bias, flat, and dark frames
  • Cosmetic Correction
  • Weighting using Subframe Selector tool
  • Registration
  • Background extraction using synthetic flats
  • Linear Fit of Green and Blue to Red
  • RGB Combination

RGB:

  • SCNR green
  • TGVDenoise and MMT noise reduction per Jon Rista's noise processing workflow
  • Arcsinh stretch
  • Histogram Transformation
  • Resample to match Luminance dimensions

LRGB:

  • LRGB Combination
  • ACDNR on chromacity to clean up some color artifacts on the stars
  • HDRMT on the bright areas of the nebula, then mixed in at 40%
  • Curves adjustment (saturation and contrast)
  • Crop and Resample for web
  • Watermark

 

 

GecHl0S.jpg

 

 

And for a larger res image see Astrobin:

 

get.jpg?insecure


Edited by pbkoden, 19 January 2019 - 12:26 AM.

  • Gregory, Joe G, buckeyestargazer and 17 others like this

#2 MikeTahtib

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Posted 19 January 2019 - 09:20 AM

Nice pic of an object that no one seems to talk about much.  I like this one,  It's subtle visually, but a fun challenge for me to find in my bright skies.  It's nice to see what it really looks like.



#3 lynnelkriver

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Posted 19 January 2019 - 10:34 AM

Very nice image!  Thanks for sharing your processing sequence also as I'm just learning Pixinsight.  Scott



#4 pbunn

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Posted 20 January 2019 - 03:40 PM

Very nice image on what I find is a difficult subject.




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