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New LDN183 and use of BlurXTerminator

Bryan Wells
in PixInsight
In the LDN183 tutorial "SPCC and Fix Diffraction Pattern Problem", you run BlurXTerminator with correction only.   And you say this is to improve the quality of the use of StarXTerminator.  Then you fix the diffraction pattern and recombine the stars with the nebula.  Then in the next tutorial, "Aggressive BXT", you run BlurXTerminator again, with different settings.  I cannot tell if the image  you run BlurXTerminator "aggressively" is the same image as the one from the previous tutorial or not.  Did you actually run BlurXTerminator twice on the same image?   I also got a bit lost on when your images becomes non-linear.  I understand the purpose of the tutorial, but I wish you made it clearer when, during the tutorial, you did certain things.  A simple timeline, showing the steps you apply from the first to the last tutorial would be a big help to me.  I keep having to go back and re-watch over and over to figure out when you do what operation and why.  

Comments

  • BlockHeadBlockHead
    edited June 2024
    Hi Bryan,

    I understand that there is confusion. However, I have to say that one issue is that people do not want to see perfect data all the time- and this is precisely the danger of using imperfect data where you need to do other things which make a more simple timeline complex.

    I assume you did see the PDF which is effectively a shorthand timeline right?

    Specifically in this case:
    ****The initial use of BXT on the RGB of all frames is more for informational purposes- to see the star artifacts and yes, potentially help SXT do its job. It isn't critical. 
    1. I generated an integrated image of good stars from a subset of all frames.
    2. Removed these stars in the linear state (throw away the nebula component) with SXT. 
    3. Removed the stars from **** above and keep the nebula. So yes, these stars with correct only BXT are being thrown out. 
    4. Add the full integrated starless nebula with the partial integrated good stars (#1). 
    5. Apply BXT aggressively to the now combined full nebula with good stars. 

    So according to the above I did not apply twice. Please keep in mind. I do not process everything completely and then go back and record everything for a second time. Although this would minimize confusion- the time investment is simply too much. So the initial use of BXT as it turned out was non-critical... 

    Regarding the non-linear- this is very important. 
    Take for example what I do to get a stretched image.
    While the RGB is LINEAR I extract the stars (these are now aggressively BXT'ed)
    Why? Because I will ultimately stretch the nebula image differently than the star image- meaning there are two stretches involved. Did you get this? Two paths... the star image is typically adjusted a little with a raised MTF (make the stars less bright with the middle slider of HT). This further de-emphasizes them if desired.

    I also show the choices for stretching and dealing with the starless image.

    Please let me know an example that is confusing so I can understand specifically.

    -the Blockhead
  • Bryan Wells
    Thank you very much for the details and this helps a lot.  I love the complexity and that too is very helpful.  But it does make it harder to follow in a linear way that my brain wants to work. Thanks for the clarification. I love your tutorials and go back to them time and time again.  I am lucky to get clear enough skies for imaging 4 or 5 times a year, and I find myself having to review and relearn but that is made harder because what I did before is often not a great fit for what I need today since no two images the same.  I am on my way to become a master if live long enough or if I retire soon! :)  
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