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Adding Ha highlights to LRGB galaxies

01 May, 2016 12:25
I'd be interested to know what methods people use in Photoshop (I don't use Pixinsight) for Ha highlights in galaxies.

I sort of worked out a method to do it, by converting the Ha to RGB and then pasting LRGB over it, blend mode lighten and then increase the red on the Ha layer.
This sometimes it works OK but sometimes it doesn't, and it doesn't always produce a deep enough red either.

I'd be interested to know what Photoshop methods others use.  I've tried googling it and all I can find it combining in nebulae rather than Ha highlights in galaxies.


01 May, 2016 13:00
Hi Carole,

usually i prefer PI to PS, but when adding HA in PS i use the following procedure:

  • copy only red channel of RGB into a new image
  • add HA to this new image (new layer) blend mode linear dodge (which actualy "adds" HA to R), adjust opacity of the HA layer (usualy very low values)
  • once happy, merge all layers of this new image
  • finally, i replace the red channel in the RBG with the new image
If this does not work for you, play around with blend modes. HTH,

Edited 01 May, 2016 13:18
03 May, 2016 22:44
Hi Carole,
after you have done what Fritz suggests, it may be that you also need to blend the Ha data into the luminosity layer. If the Ha occurs in discrete regions and there is very little Ha information in the luminosity, then it will hardly be seen in the final image. At least, that is how I think it works but then I have only tried this for nebulas…..

05 May, 2016 11:57
Blending Ha into luminosity channel is obligatory. Otherway you cannot highlight Ha data!
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