Combining 2 RGB images in PixInsight

[dlp]

I had a go at combining 2 images using PixelMath as per Juan's posting - Combining images with different exposure times & ISO values

I guess that was aimed at non-RGB images, but in any case my expression (snB=nB*AvgDev(A)/AvgDev(; A/nA/nA + B/snB/snB) fails 'Parse Error: Expected lvalue operand'.

I wonder if anyone could say what the correct expression should be, and how I input RGB noise SD into 'Symbols' ? (I used just the figure for the red channel in my test)

(I've posted this on the PI forum, but thought it would be a good idea to post here too!)

David

[dlp]

Ok, Juan at the PI forum (The man!) replied and I re-did the combine as I'd clearly made a mistake. It works fine! Below are the equations I used. I got the noise figures (nA, NB) from the Script/Utilities/Noise evaluation, but I just used the figures for the red channel as I didn't know how to 'average' the R-G-B. My Images were named A and B btw.

David