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#1
17-09-2020, 11:34 AM
 Lognic04 (Logan) Registered User Join Date: Mar 2016 Location: Melbourne, VIC Posts: 888
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
#2
17-09-2020, 11:50 AM
 glend (Glen) Registered User Join Date: Jun 2013 Location: Lake Macquarie Posts: 6,037
I could explain how to do it in Photoshop CC.
#3
17-09-2020, 11:59 AM
 Nikolas (Nik) Dazed and confused Join Date: May 2012 Location: Melbourne Posts: 1,830
In Photoshop you add HA as a luminance layer then vary the opacity
#4
17-09-2020, 12:46 PM
 Atmos (Colin) Ultimate Noob Join Date: Aug 2011 Location: Melbourne Posts: 6,873
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.
#5
21-09-2020, 10:15 AM
 Andy01 (Andy) My God it's full of stars Join Date: Mar 2012 Location: Melbourne Posts: 2,699
Marco Method...

Logan, look no further - THIS is the business
#6
21-09-2020, 11:01 AM
 Lognic04 (Logan) Registered User Join Date: Mar 2016 Location: Melbourne, VIC Posts: 888
Quote:
 Originally Posted by Andy01 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?
#7
21-09-2020, 11:02 AM
 Lognic04 (Logan) Registered User Join Date: Mar 2016 Location: Melbourne, VIC Posts: 888
Quote:
 Originally Posted by Atmos 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
#8
21-09-2020, 03:46 PM
 LewisM Novichok test rabbit Join Date: Aug 2012 Location: Somewhere in the cosmos... Posts: 9,982
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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