Problem using Harry's tutorial on an HaLRGB image

[plind]

I applied Harry's "Add Ha to RGB" tutorial to combine Ha and LRGB images of M31. (This is the "two pixelmath equation" method). Perhaps the method works only with RGB originals not LRGB, but it resulted in an output RGB image with mustard yellow Ha regions, with tinge of orange, not the red I was expecting.  I've plugged various constants into Harry's equations to no avail.  This is a mystery to me because the second equation just adds more red to the red channel, and I don't know where the mustard (yellow) came from. 

Paul Lind
(I posted this in the wrong area a couple days ago).

[MortenBalling]

Try to do an automatic ScreenStretch to the image, and see if that helps. When you start mixing channels, you often end up with a distorted color balance.

cs

Morten

[plind]

Morten,

That seems to have been the problem.  Instead of an automated stretch, I used a small controlled stretch in Photoshop by using the same RGB curve on both the LRGB and Ha images. Now Harry's method of adding Ha gives nice red Ha regions.

Thanks,
Paul

[jkmorse]

Paul,

Anything you can do in Photoshop you can do in PixInsight, only with more control.  For example, I recommend you test out the CurvesTransformation tool which is much more flexible that PS Curves.  Gotta go cold turkey on all those old safety nets.

Best,

Jim