Overlay two images

[remi@astrorl.ca]

Hi,
I would like to combine a Luminance layer with an Ha layer. I normally do this in PhotoShop using layers and overlay. How can I do the equivalent in PI? Can it be done in PixelMath and if yes, what would be the equation?
Thanks in advance.
Remi

[avastro]

Remi, search the forum for combining Ha with RGB, you will find many approach, like this one.
https://pixinsight.com/forum/index.php?topic=11526.msg71476#msg71476
cheers
Antoine

[oldwexi]

Hi Remi!
If you have Luminance image  "L" and H-Alpha image "Ha"
You can mix mix/overlay these 2 mono images/layers with different PixelMath expressions:
The simplest one is:
L + Ha

including also  percentages: 70% L and 30% Ha the expression in PixelMath is:
(L*0.7)   +  ( Ha*0.3)

etc... etc...

There should be also in your installation the script "Blend" selectable. (Utilities/Blend)
Where you find more possibilites to overlay images as you know from the astropaintings program,
without needing PixelMath knowledge.

In addition let me mention:
to mix Lum with Ha does only make sense if you stay in mono!!
Mixing the Lum+Ha result with RGB  results in wrong/pink Ha colors as Lum gets also into Green and Blue channel.
Therefore this results in typically pink HA areas...
Ha should never be imbeddeed into L when doing LRGB!
Ha should be imbedded into the R channel.

Gerald

[mmirot]

Blend is not in the current release. Still works? Have a link

Thanks
Max

[oldwexi]

Max!

Give me a few minutes, will come up with the private link.
On my installation WIN 7 Prof +  newest PI it works.

Gerald
P.S.: if you have added  in
Manage Update Repositories
http://pixinsight.com.ar/repository/
it should be available.

[oldwexi]

Hi Max!

If you click
http://pixinsight.com.ar/repository/

you can download manually the zipped
BlendStarMask script.

Gerald