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The North American Nebula - SHO (NGC7000)


paul
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This is the result of about 13hrs integration, subs were 120s @ gain 200. I feel there is more detail to extract but not sure how best to do it without adding too much noise. In the end I settled for HDR and mild deconvolution in the final stages.

NGC7000_deconv.png

NGC7000 was one of the first wide field targets I ever attempted to image way back in 2005 with a modded Toucam + SLR lens, my gear has improved just a bit:

 

image.png.f04eec866427cdb354ae7a518905943c.png

Edited by paul
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3 hours ago, paul said:

This is the result of about 13hrs integration, subs were 120s @ gain 200. I feel there is more detail to extract but not sure how best to do it without adding too much noise. In the end I settled for HDR and mild deconvolution in the final stages.

Looks great, and a big improvement over the original. With the ZWO1600 I found by using a gain of 139, and 300s subs, the noise is minimal. Another way to reduce noise of course, is to take more data. Are you processing in Pixinsight?

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4 hours ago, paul said:

This is the result of about 13hrs integration, subs were 120s @ gain 200. I feel there is more detail to extract but not sure how best to do it without adding too much noise. In the end I settled for HDR and mild deconvolution in the final stages.

NGC7000_deconv.png

NGC7000 was one of the first wide field targets I ever attempted to image way back in 2005 with a modded Toucam + SLR lens, my gear has improved just a bit:

 

image.png.f04eec866427cdb354ae7a518905943c.png

And your processing,

Roger

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2 hours ago, AstronomyUkraine said:

Looks great, and a big improvement over the original. With the ZWO1600 I found by using a gain of 139, and 300s subs, the noise is minimal. Another way to reduce noise of course, is to take more data. Are you processing in Pixinsight?

LOL, I started at the beginning of this year with gain 139 for everything while I got the hang of the gear. Gain 0 has been great for RGB LP and keeping the stars under control and amp noise down of course. I should try 139 and longer subs for NB, my tracking has no issues at this shorter focal length on the old HEQ5. And more subs always helps of course!

 

Yes, I'm using Pixinsight. For these images with lots of nebulosity across the frame I have been using ABE rather than DBE - DBE seems to clip out the fainter nebulosity no matter what I do. 

My minimal steps tend to be:

  • Dynamic Crop,
  • Linear Fit
  • Combine
  • DBE/ABE
  • Photometric Colour Correction
  • Linear Noise Reduction
  • Partial Hist Stretch in several steps
  • Starnet++
  • Hist' Stretch Starless
  • Curve Stretch
  • HDR (maybe) 
  • Saturation
  • Pixel math combine starless and star_mask
  • Deconvolution (maybe)

During the stretch phase is when I mess about with the process, sometimes I work on the starless image, other times I step the image back and apply the star_mask then proceed to process the image.  It's also the phase when I manual adjust the channel mix and remove purple and green casts.

Deconvolution nearly always brings in obvious artifacts.

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1 hour ago, paul said:

LOL, I started at the beginning of this year with gain 139 for everything while I got the hang of the gear. Gain 0 has been great for RGB LP and keeping the stars under control and amp noise down of course. I should try 139 and longer subs for NB, my tracking has no issues at this shorter focal length on the old HEQ5. And more subs always helps of course!

 

Yes, I'm using Pixinsight. For these images with lots of nebulosity across the frame I have been using ABE rather than DBE - DBE seems to clip out the fainter nebulosity no matter what I do. 

My minimal steps tend to be:

  • Dynamic Crop,
  • Linear Fit
  • Combine
  • DBE/ABE
  • Photometric Colour Correction
  • Linear Noise Reduction
  • Partial Hist Stretch in several steps
  • Starnet++
  • Hist' Stretch Starless
  • Curve Stretch
  • HDR (maybe) 
  • Saturation
  • Pixel math combine starless and star_mask
  • Deconvolution (maybe)

During the stretch phase is when I mess about with the process, sometimes I work on the starless image, other times I step the image back and apply the star_mask then proceed to process the image.  It's also the phase when I manual adjust the channel mix and remove purple and green casts.

Deconvolution nearly always brings in obvious artifacts.

Your workflow is something similar to mine with SHO, except I don't use Linear fit on SHO, I find it gives no benefit.

I do my DBE before combining, I find it does a better job if you do it on the individual mono channels, than the combined SHO. After stretching and Starnet, I will use convolution on the starless image, and crank it all the way to 10, it reduces noise dramatically, a Lum using the Ha data will be used for the detail. Then I carry on with curves, using Lum masks or the colour mask script. I take a copy of the Ha data, run it through EZ Decon, then EZ Denoise, stretch it, remove the stars, then combine with the SHO in LRGB Combine. Add the stars to the LRGB Combined image, run EZ Star Reduction. If it needs it I will use HDRMultiscaleTransform, then LocalHistogramEqualization. Followed by a tweak in curves, and run the DarkStructureEnhance script to bring out dark dust lanes.

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1 hour ago, AstronomyUkraine said:

a Lum using the Ha data will be used for the detail.

That's interesting, I've seen this step mentioned in tutorials but dismissed because this will "re-emphasize" Ha structures but  Oiii and Sii information will remain softened by convolution.  But I guess if Ha is much strong its influence on structure will be greatest. Experience outweighs conjecture so I will give it a go 🧐.

 

 

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31 minutes ago, paul said:

That's interesting, I've seen this step mentioned in tutorials but dismissed because this will "re-emphasize" Ha structures but  Oiii and Sii information will remain softened by convolution.  But I guess if Ha is much strong its influence on structure will be greatest. Experience outweighs conjecture so I will give it a go 🧐.

 

 

What you can also do, is combine all 3 SHO channels in ImageIntegration to make a Lum, that way you get detail from all 3 channels, and a more balanced Lum.

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I tried a LUM mask but must have mucked up the steps as the outcome was not good. I'm still hoping to get this right but in the meantime here is a V2. I changed the sequence of processing, basically did a custom deconv on each channel before combining, combined and then noise reduction.  This reduced the impact of the stars dramatically (the golden halo around each has gone and they stay sharp) and increased the overall sharpness. After that my same steps. I still hope to get more sharpness and contrast so I will keep at the LUM mask.

 

 

 

 

 

NGC7000_V2.png

Edited by paul
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4 hours ago, P Holdsworth said:

I also prefer the second version. lovely sharp detail and colour palette 👍

Thanks, it has stayed on my desktop the longest. Now I need consistency, you think you have it sussed then the next target proves you still have things to learn😄

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