Paul
Impressive image and you really have captured the outer material as well as the faint background galaxies, but I have a problem. Looking at Peter_4059's image of the helix, although it doesn't have the depth of your it has one feature that is missing from yours.
Look here
http://www.iceinspace.com.au/forum/s...ighlight=Helix
And within the Helix itself I see a miriad of faint stars in the 6 hr exposure that are missing from your image.
Is this because a lot of NB data to bring out the outer halo has led to the demise of these stars?
Anyway an interesting observation
Allan