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NSG + Mure Denoise = Colour Issues(?)

JK
edited May 2022 in PixInsight
Any thoughts on the following would be welcome.

I spent today trying to process M101 RGB data (15 x 5mins each) using NSG (xnml version) and Mure Denoise. All seems ok except when I channel combine the colours seem washed out - noticeably there is virtually zero blue which is odd given M101 has a lot of blue details. 

I then tried every combination of using/not using NSG and / or Mure and all of the tests worked except the ones using NSG. 

So, NSG is causing the Blue to be lost from M101.

I suspect user error, else everyone would be complaining about this, but I have spent hours trying to find a problem including several reruns and it all looks ok. 

Any thoughts why NSG, or my use of it, could be doing this?

Comments

  • You didn't happen to apply NSG across all colors did you?
    (That would do it)
    -the Blockhead
  • I applied NSG to each filter stack separately, is that what you mean? 

    I used my standard pre-process which is:

    Blink/SFS to select best subs and Ref for NSG (also check calibration frames)
    WBPP through to Registration (lights, Flats, Flat-Darks, Darks)
    NSG on each stack (Red, Green, Blue) - xnml + ImageIntegration Template.
    ImageIntegration - I usually use GESD but only 15 subs in each stack so went with Winsor that it defaulted to.
    Temp Channel Combine to get a Dynamic_Crop set up
    Crop each stack 
    Mure Denoise
    DBE
    Channel Combine

    I will have another look today, at least I have narrowed it down to NSG - perhaps its a data issue - I will go right back to blink and see if I missed something.
  • I should have mentioned the data was captured over two sessions - perhaps this is a factor.
  • I now have this working, it is too long a story to tell in full but essentially all I needed to do was tweak the STF auto-stretch which was significantly over-stretching the NSG image and blowing out the blue channel. 

    I didn't spot it initially as I used the "copy STF process to HT" trick for the initial stretch. 


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