You are quite correct Peter. It looks like a bit of backlash in the DEC axis. I agree the colour is a bit cartoony.
I upsized the image and adjusted it to something more realistic.
Here 3 MB
http://d1355990.i49.quadrahosting.co...2_RH200col.jpg
Here is the red channel with the HA I presume. 5MB
http://d1355990.i49.quadrahosting.co..._RH200_red.jpg
The stars look far better than either blue or green.
Bert