M27 Dumbbell Nebula in Narrow Band H-Alpha/OIII and RGB

M27 Dumbbell Nebula in Narrow Band H-Alpha/OIII and RGB, a photo by Urlaubsknipser on Flickr.

Via Flickr:
Comparison between a synthetic RGB made from H-Alpha/OIII and a "real" RGB taken without filters.

Even with 12nm narrowband filters it is extremely hard to pull out the outer halo from M27.

Exposures were:
200min H-Alpha 12nm,
235min OIII 12nm
with 10 and 15min subs.
Equipment: 500Da + EF 5,6/400mm L at f5,6/ISO 800, mounted on Avalon Linear.

The RGB from 2011 was made from only 92min exposures (2min subs) with same lens, but 1,4x Kenko Extender (f8,0/560mm), mounted on Astrotrac.