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IKO - SH2-155 Cave Nebula SHO - Processing Competition


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New to StarTools and composites so here's my attempt! Pretty much used all defaults with minor tweaks. Colour was sampled and applied using HST preset. Thanks for great data to 'play' with:



Edited by Dazzyt66
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I've had another go at this data set with a slightly different processing work flow and it's brought out alot more of the dark dust in the image.

This was all done in PixInsight and the work flow is as follows:

  • Dynamic Crop of the three images to make them all the same size.
  • Channel Combination to create a new SHO image then performed basic ABE, ColourCalibration and Background Neutralisation. 
  • Binned x2 then STF stretch followed by StarNet for star removal.
  • On the star layer, I used the CorrectMagentaStars script and reduced the stars by 20%.
  • Opened the original Ha layer and performed ABE, then STF stretch and StarNet.
  • RGB Curves to get the brightness & detail I wanted before adding this layer as a Luminance layer to the SHO image using LRGBCombination.
  • Curves to bring out the colours and detail in the darker dust. Some of the background on the left of the image was a bit purple, so applied the CorrectMagentaStars script a couple of times to correct that.
  • 8 layer MultiscaleTransformation and a bit of UnsharpenMask.
  • Then added the stars layer back in using PixelMath and resized the image.


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Here's my entry, processed in Pixinsight and Photoshop. STF stretches, then Starnett on each of S, H and O, into Photoshop to deal with Starnett artefacts, combined as SHO in Pixinsight, combined Starry Ha as Lum using Pixinsight LRGB, selective colour in Photoshop, a bit of star reduction,  Local Histogram Equalisation, sharpening, noise reduction, rotate and crop.




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My word i struggled with this. Then again i've only just managed to start get decent results processing the moon. A nice way to spend several hours away from work.

Uploaded the .fits into Affinity Photo added recolour exported as .tif. Loaded the .tif into Siril and ran colour photometric colour calibration (really struggled to get any blue), ran histogram and a little play in Photoshop.






Edited by Dean Hale
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This is processed with PixInsight. 

  • Started with Deconvolution and Dynamic Background Extraction on each channel. 
  • Combined the channels with Pixel Math using the expression R=(0.2*Ha)+(0.8*Si), G=(0.8*Ha)+(0.1*Si)+(0.1*Oiii), B=(0.1*Si)+(0.9*Oiii).
  • Extracted the lightness channel from the combined images as the Luminance channel to add back in after the color image is made to enhance the details. Then used the Dark Structure Enhance script to subtly enhance the contrast in the dark nebula areas
  • On the color image I removed most of the purple using the magenta mask option of the Color Mask script.
  • I used Starnet to separate the stars and nebula and used just enough Convolution to smooth the specific areas where starnet left artifacts. 
  • On the nebula image I used two iterations of applying the cyan, green, and yellow mask options of the Color Mask script and used Curves Transformation to adjust the color, saturation, hue, lightness, contrast, and a-b-c components of each iteration. 
  • The Exponential Transformation tool was used with the Lightness Mask checked to increase the brightness and contrast of the very faint details. 
  • I made 4 masks using the Range Selector and Curves Transformation processes with progressively less dark nebula selected so the smallest dark structures would receive the most sharpening using the Unsharp Mask tool.
  • On the star image I used SCNR (Subtractive Chromatic Noise Reduction) to remove the purple and green colors from the stars and added saturation with the Color Saturation process.
  • The star and nebula images were recombined using the StarNet expression Nebula+(0.6*Stars) and then used Convolution to soften the chromatic noise.
  • The Luminance image was merged with the color image using the LRGB Combination process.
  • I used HDR Multiscale Transform to bring out even more detail in the dark nebula and then made the final fine contrast adjustments with Curves Transformation.

Thank you for the competition. I really enjoyed working with the great data.


Cave Nebula.jpg

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Being treated again with lovely data, thank you.

This is a first pass to see what the image was, I hope to reprocess at a less aggressive bin % and update this image but I wanted to share what I had done.

StarTools 1.8.515a compose | crop | bin 50% | wipe | aautodev | HDR | colour [SHO 40SII+60Ha,70Ha+30OIII,100OIII] | shrink | denoise


Edited by happy-kat
v0.3 substituted
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Here are my two versions, I realised just now that I missed the cut-off, frustratingly I finished them a few days ago but didn't get around to uploading, but anyway....

  • Remove haloes around the bright star in PI on OIII and SII
  • Decon each filter
  • Make Synth Lum using Image Integration
  • Stretch each filter
  • Remove stars from each filter, reduce stars on Lum
  • In PS, colour tones, topaz denoise AI, local contrast
  • Create separate HSO image for stars, adjust colours
  • Combine these stars with the SHO and SHOO images in PS 
  • Use Noel Carboni's actions to slightly soften the images
  • Final adjustments in Lightroom to colours and some local adjustments





Edited by Jon2070
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  • 2 weeks later...
On 28/09/2021 at 19:47, Budgie1 said:

I'll kick this one off then. :D

Beautiful data again, didn't even bother with noise reduction on this one!

So, this is an SHO rendition using PixInsight only. A slight crop, then ABE, followed by the stretch and Starnet.

Worked on the stars to give a more natural look, used the CorrectMagentaStars script and then a little CloneStamp to remove some yellow centres to the larger stars. A slight star reduction and that was about it.

Moved on to the nebula: Started with easing the saturation with several attempts, then enhance the blue, used CIE b* to enhance the blue & yellow then the lightness to bring out the dark dust clouds. Finally played around with UnsharpMask to bring out more detail. Then PixelMath to recombine the background & the stars and resize. 


Yea this is why I’ll never be able to do astrophotography 

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  • 10 months later...

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