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9 July 2020 - APP 1.082 has been released which contains one important bug fix. 1.082 has full Fujifilm RAF support, so that includes SuperCCD & X-Trans camera's 🙂 !

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[Sticky] HaRGB and LHaRGB workflow and star color calibration  


Quasar Admin
Joined: 3 years ago
Posts: 1913
May 31, 2020 15:27  
Posted by: @hyperion

I try to process my data from m51.

My files  are R G B and HA from OSC 

Everything going normal before Star Color Calibration after this my data taking a reddish color and i cant get over it ...

 This is Before star Color

Be4 Start Color  Calibration

And this is after


After Star Color Calibration

Any Help will be appreciate  it ... 

If someone want i can upload my data to check it ...

Many thanks.


Dear Stratos @hyperion , @vincent-mod, @astrogee, @sda ,

Thank you Stratos for sharing your data with us 😉 I have had a go myself since I am actually working to improve HaRGB and LHaRGB composites for a future APP release.

The workflow to do star color calibration on a HaRGB (or a LHaRGB) is not recommended, in fact it is physically a wrong step. You need to do star color calibration on broadband data. If you add narrowband data in the mix and then try to perform star color calibration on a broadband+narrowband composite, it would be mere coincidence if the colors look good...

Star color calibration needs broadband data to make sense of the star color physics. Adding narrowband data in there will cause the R/G B/G ratio's of the stars in your data to be polluted by the narrowband signals. Those narrowband signals don't follow the physics at all that we use for star color calibration.

So how to do this properly then?

1) create a RGB (or LRGB compositie), in this case I used formula RGB 2 in the RGB Combine tool

2) perform Remove Light Pollution and Background Calibration on the RGB composite ( ! if you perform Remove Light Pollution, you automatically perform Background Calibration, there is no need to do it again after Remove Light Pollution)

3) Perform Star Color Calibration on this RGB composite that is corrected for light pollution and is background calibrated:

RGB2 formula LPC CBG SCC

4) We know open the RGB Combine tool and will add the H-alpha layer. Now, these next 2 steps are essential to preserve the RGB Star Color Calibrated colors in your composite:

  1. set normalize to none in the RGB Combine tool.
  2. Load the RGB star color calibrated result into the tool with the RGB 1 formula

These 2 steps will preserve the colors of the star color calibration 🙂 !

5) Add the H-alpha layer in the RGB Combine tool.

RGB2 formula LPC CBG SCC add Ha layer

6) To preserve the colors and luminance of your star color calibrated result, set the luminance for the composite so that it is preserved. Normally you want Red to contribute for roughly 20%, Green for 70% and Blue for 10%.

7) And slightly add H-alpha to red, I added it for 23% to Red as can be seen in the below screenshot. Now to maintain the star colors, you need to gently adjust the multipliers for the R,G,B channels as can be seen as well. Red 1,15, Green 1,17, Blue 1,20. These factors do depend on the data, you need to do this carefully. Try to get the same colors as the star color calibrated result off course 😉

RGB2 formula LPC CBG SCC add Ha layer finished

I am working to make this more automatic and easier for the user off course, but this is a proper workflow in which you can get good star colors with narrowband included to enhance the active regions in this case of M51 😉

This show the star color calibration result next to the final HaRGB composite: we see that star colors are still good and we also see much more enhanced active regions in M51 from the H-alpha data, top is the RGB composite after star color calibration, below is the finals HaRGB composite with the same star colors 🙂 :

RGB versus HaRGB star colors maintained

Let me know if this is clear and/or if you have any questions about this workflow 😉

Crop of the field of view of the final HaRGB:

M51 HaRGB Stratos Mabula crop




This topic was modified 1 month ago by Mabula Haverkamp - Admin

Brown Dwarf Customer
Joined: 2 years ago
Posts: 6
June 3, 2020 22:14  


Thanks for the work flow Mabula

I placed rgb composite with star color calibration etc in the combine , rgb 2 in fits

Than i did a combine with the load Ha and O3 and no check on force bayer. also in fits

When i placed this stack in combine rgb1 and clicked combine i got that the depth and fit were incompatible and i could not get a combine of the processed RGB and the Stack and processed Ha, O3  { the L-enhanced ] filter

What am i doing wrong?

I have to say that with theL-enhance filter doing a regular OSC processing and finiishing in Photoshop with Starzonia plug in i get good results. So can i improve this action with this work flow if you can give me a clue as to what i am doing wrong

Thanks  Stuart Meyer md




Main Sequence Star Customer
Joined: 1 year ago
Posts: 33
June 6, 2020 15:48  

My way of processing ...

Mabulas Workflow is the best that i used until now...

Thanks Again ...

Clear Skies .

Stratos S.




Brown Dwarf Customer
Joined: 2 years ago
Posts: 6
June 13, 2020 23:16  


Does that mean that I cannot use my l-enhance filter when I gather my RGB data with a OSC.

Correct me please ,,,As I understand this I should take RGB data and process. Than take another set of data with the L -enhance filter and process as Ha and O3 .

and place in RGB combine????

Quasar Admin
Joined: 3 years ago
Posts: 1913
June 14, 2020 12:46  

You can yes, you can place a narrowband filter on your OSC camera, the only difference will be that you need to expose longer as there's less sensor available to capture the specific wavelengths that your filter is letting through. With a mono sensor, the entire sensor can be used.

So what you do is to capture RGB data without filter (or one that still lets through most of that data) in one session and in the next you add the filter you want and take that data and then you combine that later in RGBCombine using a specific workflow.