Combining Ha and OIII narrow band

[niteman1946]

Hi Group,
I am imaging M27 using both the Ha and OIII filters.  My intent is to combine these and use this combination as my Luminance.  Then add RGB for the color.  My reason for using both narrow bands is there is quite a bit of different info in each that is worth preserving.

I had raised this question a few years back and got responses from Rob (pfile) and Gerald (oldwexi), among others.

Rod had suggested balancing the OIII to the Ha using the Linear Fit process.  And I do believe I can see a benefit in that when doing a simple addition in Pixelmath.

Gerald had cautioned that Ha was not a good source for luminance due to the "salmonizing" effect when adding RGB.  I don't dispute this.  But as I previously mentioned, there's good data in the M27 Ha and OIII, and I'd like to capture both.

So if Gerald is listening, I want to ask if there is a better way to combine the Ha and OIII than just a simple Ha+OIII in Pixelmath?

And I welcome comments and suggestions from all.

Thanks,
Mark

[oldwexi]

Hi Mark!
For objects with enough OIII and Ha light  i create the RGB image out of these two.
Ha into R, OIII into G and OIII into B with percentage increase in B.
This gets me nice RGBs with high contrast and dynamic. Adding RGB
may improve a little the star colors but will decrease the contrast of the nebula.

You can still pull afterwards L out of this combination, but the issue i mentioned last time
is still the same.

Gerald
 

[niteman1946]

Hi Gerald,

I really appreciate the response.

Yeh, that looks promising.  I will collect more time on both filters and push forward with your suggestion.

And follow-up with the results.

Thanks,
Mark