Thanks for that Rick.
I took your advice, but added to it a bit. On the cloned image I did a star mask on it as well and wiped out the stars. Then when I used it as a mask on the RGB version, the red manipulation left the stars alone.
Here's my quick attempt this morning. To improve it, I think I'd have to get the star mask more refined (I just took defaults for this from memory).
Astrobin:
http://astrob.in/121889/B/
P.S. I like how the small dark bit in the centre looks like another horse head.
