Pixel Math to combine stars and bright nebulae with starless bg file

[Rudy Pohl]

Hi There,

I am trying to combine two images in a controlled manner in Pixel Math.

Image #1.
In the first image I have removed the stars, smoothed the interstellar dust, saturated the colours and made the whole more contrasty. The overall image is darker than Image # 2.

Image #2.
In the second image I have processed it so as to leave the stars as small as possible and have added some brightness and colour saturation to the nebulae.

Combining images:
I am currently combining these two  images using a simple addition formula in Pixel Math whihc is ... image1 + image2, and various multipliers like image1*3 + image2.
I have also been using Gerald Wechselberger's formulas from his video entitled "How to enhance Nebula without pushing the stars".

However, I would like to be able to combine my darker starless image with only the brightest parts of the image with the stars, which would mean adding only the stars and the brightest nebulae and brightest dust areas.

Is this possible and what formula(s) should I try?

Thanks very much,
Rudy

[ngc1535]

Rudy,

I have found that LinearFit will likely help with making the images similar. It does work better if you have the images in the linear domain first.
Then, once you have adjusted the images (perhaps custom stretches for each)- blending them together is no problem either through weighting (the multipliers) or using things such as the screen blending algorithm (a personal favorite technique that I find very powerful).

-adam