Incorporating Ha into RGB Images - Forums

Topic starter

19 days ago

I am still pretty new to mono imaging and it’s techniques, and processing overall. I’ve seen many different ways to incorporate H-alpha into RGB images. I’ve followed an old PixInsight guide of combining H-alpha with the red channel using pixelmath, as well as using continuum subtraction with scripts that combine this result with the RGB image. I recently attempted to use Ha as luminance as well. These have all had varying degrees of success, likely hindered by user error and my general lack of data due to the unpredictability of Great Lakes weather.

I am curious as to how all of you go about combining H-alpha data with your RGB images. I know this has a lot to do with what your goal is with the image, whether it be highlighting specific lines, accuracy, or just creating a pleasing image. I intend to incorporate any advice into my future long, single target projects I’ll be sticking to as my “new target fever” subsides. Any techniques, advice or comments are greatly appreciated. Clear skies!

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Dave Stearn

19 days ago

I use OSC so I use Continuum Subtraction on Pixinsight under Script - Tools. After that I use the Ha to RGB script written by the same author. You need to have the Ha and RGB linear starless and the RGB should have SPCC applied to it first.

ScottF

19 days ago

I use the Ha to RGB script as well.

andrea tasselli

Frequent contributor

19 days ago

Dave Stearn:
use OSC so I use Continuum Subtraction on Pixinsight under Script - Tools. After that I use the Ha to RGB script written by the same author. You need to have the Ha and RGB linear starless and the RGB should have SPCC applied to it first.

Neither exist under "Scripts".

Dan Watt

19 days ago

This is the best method I’ve used to date. PhotometricContinuumSubtraction by Charles Hagen. Charles writes out how to do it all manually here:

https://www.nightphotons.com/guides/advanced-narrowband-combination/

And he also published a script you can add to Pixinsight to simplify the process.

https://www.nightphotons.com/software/photometric-continuum-subtraction/

Jakob K.

Topic starter

19 days ago

Dan Watt · Nov 6, 2025, 09:50 PM
This is the best method I’ve used to date. PhotometricContinuumSubtraction by Charles Hagen. Charles writes out how to do it all manually here:
https://www.nightphotons.com/guides/advanced-narrowband-combination/
And he also published a script you can add to Pixinsight to simplify the process.
https://www.nightphotons.com/software/photometric-continuum-subtraction/

Thanks. I’ll look into them and give them a shot. I’ve previously used SetiAstro’s Continuum Subtraction Utility script with the NBRGB Combination Script. At first glance this seems like a similar workflow. I’ll try Charles Hagen’s workflow when I process the rest of my IC1396 data.

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Bob Lockwood

19 days ago

andrea tasselli:
Neither exist under "Scripts".

You are correct, you need to go into Script then down to Toolbox. Both are in there, at least in my version of PI.

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Jakob K.

Topic starter

19 days ago

Bob Lockwood · Nov 6, 2025, 10:11 PM
andrea tasselli:
Neither exist under "Scripts".

You are correct, you need to go into Script then down to Toolbox. Both are in there, at least in my version of PI.

You’re referring to the “ideviceapps” kit I presume? One would need to add the repository to see them.

Bob Lockwood

19 days ago

If you're referring to this, then yes. Been a long time, I guess that's where they came from. I also don't use them.

Quinn Groessl

IOTD Staff

19 days ago

I’m not going to be at home much the next week or so so I can’t share my process icon that I have set up for oiii, ha, SII.

I use “Method 1 - Synthetic Color Flow Method” from this website. Night Photons - Continuum Subtraction

HR_Maurer

IOTD Staff

18 days ago

I didnt use continuum substraction so far. Maybe i’ve been trying and it didnt come out like i exspected, but that’s already some time ago.

What i do, i build a RGB image from my HII mono frames, using Pixel Math.
I use something like that, dont exactly remember the value of x. Maybe in the 0.2 range:
R: HII
G: median(HII)
B. x*HII + (1-x)*median(HII)
Then i do a background neutralization, and that’s pretty much it. The resulting RGB image is then screened into the rest. Maybe some Luminance tweaking.

Peter

18 days ago

Dan Watt · Nov 6, 2025, 09:50 PM
This is the best method I’ve used to date. PhotometricContinuumSubtraction by Charles Hagen. Charles writes out how to do it all manually here:
https://www.nightphotons.com/guides/advanced-narrowband-combination/
And he also published a script you can add to Pixinsight to simplify the process.
https://www.nightphotons.com/software/photometric-continuum-subtraction/

Thank you so much for the 2 links. They are new to me and will be using them in my imaging sessions.

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Quinn Groessl

IOTD Staff

15 days ago

Quinn Groessl · Nov 6, 2025, 11:23 PM
I’m not going to be at home much the next week or so so I can’t share my process icon that I have set up for oiii, ha, SII.
I use “Method 1 - Synthetic Color Flow Method” from this website. Night Photons - Continuum Subtraction

So I’m home now and got my process icons set for this. There’s three of them. One for each, Ha, Oiii, Sii. If you click on the D and read the description it kinda walks you through it. It’s all originally from the website in my original reply that I quoted above. They just only walk through Ha, and so I thought it would be useful to have one for Oiii and Sii as well. So if you get stuck, read through that as well. Google drive link to the process icons set.

https://drive.google.com/file/d/1YhkkvXbHzWgOo7khzDLsX2qS-T89Ha8P/view?usp=drive_link

Clicking that will bring you to a big text thing. You have to downlaod it and then run it from there. It’ll open up Pix with those process icons.

John Hayes

Frequent contributor

15 days ago

The basic concept of adding Ha to a RGB image is to first subtract a scaled amount of the R channel from the Ha channel in order to remove the broadband contribution. You’ll know it works because with the proper scaling factors, unsaturated stars in the Ha data will be (mostly) removed from the data. Then a fraction of the Pure_Ha data can be added to the R channel and 20% of that can be added to the blue channel in the LRGB result. You can read a nice write up about this technique by Martin Pugh here (highly recommended reading if you are just getting into this): http://www.arciereceleste.it/tutorial-pixinsight/cat-tutorial-eng/85-enhance-galaxy-ha-eng.

Using Charlie Hagen’s PhotometricContinuumSubtraction script and his NB combination tool greatly simplifies the process that Martin and Vincent came up with.

John

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Jakob K.

Topic starter

15 days ago

John Hayes · Nov 10, 2025, 09:03 PM
The basic concept of adding Ha to a RGB image is to first subtract a scaled amount of the R channel from the Ha channel in order to remove the broadband contribution. You’ll know it works because with the proper scaling factors, unsaturated stars in the Ha data will be (mostly) removed from the data. Then a fraction of the Pure_Ha data can be added to the R channel and 20% of that can be added to the blue channel in the LRGB result. You can read a nice write up about this technique by Martin Pugh here (highly recommended reading if you are just getting into this): http://www.arciereceleste.it/tutorial-pixinsight/cat-tutorial-eng/85-enhance-galaxy-ha-eng.
Using Charlie Hagen’s PhotometricContinuumSubtraction script and his NB combination tool greatly simplifies the process that Martin and Vincent came up with.
John

I’ll be sure to give this a read. Thank you!