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Old 17-09-2020, 11:34 AM
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Lognic04 (Logan)
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How does everyone combine Ha into RGB?

Hi All,
For the most part I have been combining my Ha data into RGB via pixelmath: (Ha*0.5)+(R*0.5), however lately I feel this is not the best way to do it - it seems to squash the natural colours while not really bringing out the detail that is expected in Ha. Would anyone care to share their methods of combining Ha into LRGB?
Cheers,
Logan
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Old 17-09-2020, 11:50 AM
glend (Glen)
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I could explain how to do it in Photoshop CC.
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Old 17-09-2020, 11:59 AM
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Nikolas (Nik)
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In Photoshop you add HA as a luminance layer then vary the opacity
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Old 17-09-2020, 12:46 PM
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Atmos (Colin)
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Although it does depend on the data and object a bit as to whether I do it during the linear stage or not but usually I'll stretch both the RGB and Ha data separately, get their histograms similar and then run in PixelMath R*R+Ha*(1-R) on the red channel.

What this does is keep the brighter regions mostly R (especially for stars) but the fainter regions become more and more Ha dominant. This particular expression doesn't work while in linear, sometimes I'll do a LinearFit on Ha using R as a reference and then use the Max(R,Ha) expression which just takes the brighter nebulosity of Ha and adds it into the R. It isn't always as neat though as it sometimes doesn't make the stars look that nice; they like they don't match the nebulosity.
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Old 21-09-2020, 10:15 AM
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Marco Method...

Logan, look no further - THIS is the business
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Old 21-09-2020, 11:01 AM
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Quote:
Originally Posted by Andy01 View Post
Logan, look no further - THIS is the business

Thanks Andy!! Looks to be quite useful! Only thing is, it doesn't seem to bring out any dust/detail that you would normally associate with Ha signal? Or is that intentional?
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Old 21-09-2020, 11:02 AM
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Lognic04 (Logan)
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Quote:
Originally Posted by Atmos View Post
Although it does depend on the data and object a bit as to whether I do it during the linear stage or not but usually I'll stretch both the RGB and Ha data separately, get their histograms similar and then run in PixelMath R*R+Ha*(1-R) on the red channel.

What this does is keep the brighter regions mostly R (especially for stars) but the fainter regions become more and more Ha dominant. This particular expression doesn't work while in linear, sometimes I'll do a LinearFit on Ha using R as a reference and then use the Max(R,Ha) expression which just takes the brighter nebulosity of Ha and adds it into the R. It isn't always as neat though as it sometimes doesn't make the stars look that nice; they like they don't match the nebulosity.

Thanks Colin - That seems really useful especially for bringing out the faint dust. Maybe a combination of these two (Marco and this) methods could be interesting... Props for a pixinsight only combination
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Old 21-09-2020, 03:46 PM
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I know it's a PS routine, but Starizona has 2 good methods. It's basically the same as Marco's too, and considering how delightful Marco's images are, I'd be paying attention. PI doesn't do everything perfectly.
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