Outer layer of Messier 57 The Ring Nebula

[stevewanstall]

This image is based on 114s subs, with around 8 hours  in Red, 4 hours in Blue and Green.  I have an earlier post on here where I asked for help because I was having trouble processing the data (less of it then). Now I have been able to process it more, with using screen invert mask to try and show the outer layer more clearly. What I cannot work out is why it is green !  Other images I have seen show it as red, but I cannot see where the green comes from, though in the histogram in PS, the red channel becomes much broader than the blue and green. Anyway, this is at the limit of my processing skills and is the least weird looking one I can come up with!. I attach the stacked  files if anyone wants a play. I have only calibrated with flats.

Ball.TIF Gall.TIF Rall.TIF

[MarkAR]

Well done with picking up the halo, could it be colour inversion from the mask ?

[stevewanstall]

I dont think so, it was green before I used a mask to try and 'enhance' it.