Methods of incorporating Ha into RGB or Luminance

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George Hatfield avatar
I came across a relatively new method of incorporating narrowband data into RGB and luminance images.  Charles Hagen developed the method which he describes on his website (https://www.nightphotons.com/guides/advanced-narrowband-combination).  It is dated November 2022.  I've tried it, and it seems to work well, but I have not seen other references to this method other than Mike Cranfield's presentation on TAIC earlier this year (https://www.youtube.com/watch?v=jeXa3gF3C_0&t=9s).  It involves using ColorCalibration to prepare an image of Ha lacking broadband data, along with Pixelmath methods to incorporate it into the red or luminance channel.   I like this method since it does not require guessing as to the magnitude of multiplication factors to use in Pixelmath expressions designed to remove red channel "contamination."  

Question...  Has anyone else tried this method of incorporating Ha into RGB and/or Luminance?  And if so, did it work as described?

If not, what is your preferred method?  

George
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Brian Puhl avatar
I've been using his methods for awhile.     He taught me first hand when I produced this image.     Love the technique honestly.   "Jimmy" as we call him is a whiz at pixinsight, and a wealth of information.   He honestly needs to produce more guides.

https://www.astrobin.com/trmt94/
Scott Badger avatar
I’ve yet to come up with a single process/workflow for adding Ha that I’m happy with, especially for galaxies, so I usually use this method plus the more traditional version plus some concoctions of my own (like simply using pixel math to blend Ha with lum/red by picking the highest pixel values between the two) and then start blending them. I’ll usually throw a straight LRGB into the mix, and sometimes an LHaGB even…..anyhow, I’ve found it tricky keeping the Ha from either overrunning other colors, or looking oversaturated and pasted on top, and blending different versions helps (sometimes…).

Cheers,
Scott
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Bob Lockwood avatar
I have a somewhat different approach than what is described above as I don't use PI, probably never will, too much Algebra involved.  I only use Photoshop, CCDStack and sometimes a little Topaz, maybe not the best, but it seems to work pretty well for me so far. As for the question, for pretty much all my HaRGB or HaLRGB images I just sum the red and Ha into one channel and use it as red. For me, I had issues with adding just the Ha later and having it turn almost all the red a pinkish color, using the combined HaRed stopped that from happening. For the Hargb images I just use the Ha as the lum layer. The only example I think I have hear on Astrobin is my image of IC63. Not sure if this will help with anyone else, but it works for me.
IC59/IC63 The Ghost of Cassiopeia ( Bob Lockwood ) - AstroBin
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jeffreycymmer avatar
I just watched a video by Bill Blanshan concerning this subject.  I haven't tried it out yet.  He has several scripts that I've found useful.  You can check him out at AnotherAstroChannel - YouTube Bill Blanshan

Jeff
Scott Badger avatar
I'll check out the Bill Blanshanvideo, I found his star reduction video to be very helpful.

I have to come clean regarding the Charles Hagan method linked to above..... I had used the first part of his continuum subtraction method to create a stripped down Ha, but then I reverted back to the more traditional method of adding it back to Red and Lum.....not sure why exactly, maybe mixing it into all three channels seemed complicated....or stretching everything before adding the Ha seemed odd.... Anyhow, I just tried using his complete method on an M82 image I'm working on, and now I feel like I need to go back and re-work a bunch of previous images!.....Ha! One issue I had though, was stretching the HaMinusLum image enough to show the fainter detail and not have the core area blown out when I combined it with the Lum, so I combined the HaMinusRed image with the Lum instead. Haven't put it up yet on AstroBin, but here's where I'm at so far.

Cheers,
Scott
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jeffreycymmer avatar
There's also a Pixinsight script called NBRGBCombination.  I've used it and it worked well.  It takes some tweeking.   It was in version 1.8.8.7 according to Juan.
Jeff
Wei-Hao Wang avatar
I think it will work the best for most people if PI has a tool that does HaRGB (and even LHaRGB) with a slide bar to control the Ha fraction and (nearly) real-time preview of the effect, while maintaining the overall color balance when the Ha fraction is changed.  It's surprising that such a tool doesn't exist in PI while so many people constantly ask how to do it, for years.

I am not a PI person (although I do calibration and stacking in PI). I can do almost what I said above with PS.
Freddy Meiresonne avatar
I use Ha as Luminance and add RGB color. But i don't use PI for processing.
I use Startools and in most cases i can work something out that is descent. But at times i have issues with too much magenta coloring on the emission nebulae..
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