Thanks Greg!
Ron - I hadn't thought of it as being like a cave, but now you mention it I can't stop seeing it
I've added more black around the borders to further enhance the effect on various print versions I'm trying out.
Troy - Thanks! Yep, I see what you mean about the airglow. I'm hesitant to remove it since it's a "natural" part of the scene. I was surprised that Barnard's Loop etc was picked up... I guess 5 min exposures on wide angle lenses really sucks in the photons. No stacking, darks, or flats involved at all - the temperature was around 15 deg C with a slight breeze, so the 5DmkII managed to keep the noise surprisingly low even for ISO 1600. On the other hand, the dark frames are shockingly bad on calm, humid 30 deg C nights.
Lester - Thanks! I was lucky with ultra dark skies and cool weather. I'm planning on getting a cooled mono CCD with a 8300 chip, but unfortunately in some ways it feels a bit like a downgrade from the 5DmkII! The 5DmkII is just awesome for portraits and landscapes
I think expectations on Canon will be very high for a mark III model...
Doug - Cheers! I'm not sure I follow what you mean... did you mean larger as in field of view or pixels in the image?
Roger - Thanks! The banana effect is from the naked-eye-like projection of the spherical night sky onto a 2D image, i.e. by the time that I'd finished shooting the Milky Way looked like a banana (or rainbow) in the sky. The weird effect comes from the extreme field of view - the field of view is over 180 degrees horizontally with a rectilinear projection... you might be more familiar with seeing fisheye projections for 180 deg FOVs?
I agree about the black areas... unfortunately, I'd planned the shoot in my head and missed the black areas before they sunk below the horizon. Ideally, this would be nice to do over several nights leading up to new moon - so everything can be captured at 0 declination.