HaRGB Processing

[themongoose85]

I am trying to process some HaRGB data and get a realistic representation of the color while keeping the high SNR and detail from the Ha image. Obviously simply using the Ha as Lum does not work and completely messes up the colors. Before anyone links to Vicent's tutorial on using continuum maps I have seen and read through it multiple times. It is quite confusing to follow exactly what you need to do and I wish it was written better to understand the exact steps required. No mater what I try the results are absolutely nothing like what that guide shows. I can't even get past creating the continuum map. It always looks nothing like what he has in his guide. Even trying to apply heavy NR like he says doesn't produce the expected results and only certain portions of the image appear to have the NR applied. I don't know if it is my data or what but using that guide just does not work for me. Does anybody have a step by step guide on how they typically process HaRGB images? I have searched all over these forums and elsewhere and never seem to find anything useful other than links to Vicent's continuum map guide.

[pfile]

the script called NBRGBCombination implements vicents method for adding Ha to an RGB image. check under Script > Utilties.

rob

[aworonow]

One very simple approach, maybe lacking the sophistication of Vicent's tutorial on using continuum maps, but easy and reliable, is to use LRGB combine. Starting with the combined/stretched (i.e., non-linear)/at least partially processed RGB image and a stretched/and perhaps processed Ha image, set the L = your Ha image and uncheck the RGB image boxes. Drop the LRGB triangle on the RGB image. Toy with the saturation and lightness to taste and repeat the triangle dropping.

Alex

[themongoose85]

the script called NBRGBCombination implements vicents method for adding Ha to an RGB image. check under Script > Utilties.

rob

Thanks rob. I've used that script many times before. My main issue is creating a high quality Lum from the Ha that doesn't destroy the color when combining with the RGB image. I just tried using this guide and still combining the Lum with the RGB destroys the color and stars leaving an ugly pink mess behind nothing like what the RGB looked like prior.

http://www.lightvortexastronomy.com/tutorial-combining-lrgb-with-narrowband.html

[themongoose85]

One very simple approach, maybe lacking the sophistication of Vicent's tutorial on using continuum maps, but easy and reliable, is to use LRGB combine. Starting with the combined/stretched (i.e., non-linear)/at least partially processed RGB image and a stretched/and perhaps processed Ha image, set the L = your Ha image and uncheck the RGB image boxes. Drop the LRGB triangle on the RGB image. Toy with the saturation and lightness to taste and repeat the triangle dropping.

Alex

Thanks Alex. This does not work as the color from using the Ha as Lum is completely ruined after combining them.

[jkmorse]

Another tool that I regularly use to add Ha data to my images is the SHO-AIP script.  It provides enormous flexibility in how you mix the colors so you can alter the red/Ha mix of the red channel repeatedly until you get the look you want.  Just one more option in the PI toolkit.  The steps below are from my workbook and, though they apply to narrowband filters, they also work with HaRGB images:

Option II (Using SHO-AIP script in non-linear phase)
This is another powerful color mixer that deserves your attention.  This is now my go to method for processing NB images and I often use it instead of LRGB Combination as well.  One of the best features is its built in creation of a SynLum as a part of its process. (Note: if you read French, which I, much to my chagrin, do not, it may help since there are hints available in French in this post: http://pixinsight.fr/mixshonrvb.html)
Note, per a PI Forum discussion thread, you are to use this tool in the non-linear phase of your processing.
Here is a translation from one of the SHO team videos (generously donated by Jeryyyy in this post: http://pixinsight.com/forum/index.php?topic=8706.0 which post is well worth reading in its entirety) Note:items in red in [xx] are my adds:
1.   Try to equate the three images for background darkness and star size.

2.   Open the script and create the L.  Their suggestion is 100% H and 60% S.  Try different "method" of mixing and look in areas where you want nice gradients.... you can try many different methods.  They use "Light or Linear Light" in the video.  Hit the button to make the image and you can close the script.  [Note 1: If you are using the tool for an RGB set, use all three images at 100% to build the SynLum][Note 2: keep in mind that if you want to create the SynLum in the linear phase so that you can take advantage of deconvolution, for example, you can avoid this step and simply sub in your own SynLum for the L in the step below.]

3.   Call the created image "L" and mess with stretching etc to get out the detail you want to get. 

4.   Rename the images L S H O.

5.   Reopen the script and it finds the renamed images automatically, then you go to the bottom to the color Layer to Mixing.  R=S at 100% G=H at 80% and B = O at 100%... in the video.  [Note that I do not use these settings, instead going with the setup I referenced above, namely Red: 80% SII & 20% Ha, Green: 80% OIII, 20% Ha, Blue: 100% OIII.  You get the detail of the HA in the SynLum without it overpowering the other colors in this mix.]

6.   Then go up to the L-SHO controls and push the L button (Ever use PhD guiding... Push Here Dummy). 

7.   Et, comme on dit en francais:  Voila! 

8.   Now there are lengthy French commentaries worthy of the Impressionists about getting color balance right, not too much of one and not too much of the other... but the important point is that you can mix values from all three narrow band images into each of the three colors... mix and match (this is way cool).  Each time you push the button you see the new color mix. 

9.   Then, of course, you can push the R button to add the L.  They have their own method for doing this using the check off box.  The alternative unchecked seems similar to regular LRGB combo. Here I had trouble with the linear image and I think I have to get the L stretched earlier in the process. 

10.   The end of the video talks about how to reduce star color... need to listen again.... and states that if you do this linear you have to check all the boxes at the top to get the autoSTF... the video was carried out in stretched images and I think that says a lot about the optimal choice for this method.  You can save your settings and load them for similar SHO images in the future.

Best,

Jim

[themongoose85]

Awesome thanks Jim. I will take a look at this tonight and see what I come up with. I know that this isn't a realistic approach over using actual Lum but hopefully I can get a workflow that gives close to the results I want.