Nice one George,
There appear to be a few different approaches to combining Ha & RGB.
Starizona method-
https://starizona.com/acb/ccd/software/ps_hargb.aspx
Marco's method-
http://www.iceinspace.com.au/forum/s...d.php?t=138473
Pixinsight (ask Rick!)
Personally, I prefer Marco's method, works ok for me anyway!
Cheers
Andy