Try something more easy: use the green channel of a RGB as luminance. the blue channel of a RGB as blue and use Halfa as red channel. And process as bi-color, similar to Hubble palette
See the tutorial from Ken Crawford
Clipping Masks and Color Mapping for Narrowband Processing
in
http://www.imagingdeepsky.com/Presentations.html
Why not ?
I tried,
without great success, with M 8. I used a RGB photo and I played with it:
http://astronomia-e-astrofotos.10697..._rabble_k5.jpg
The original post with all them:
http://astronomia-e-astrofotos.10697...013-td993.html