Helix Nebula (NGC7293)
Seven good-quality frames were captured at Verendrye, a dark site (grey/black LP), and combined with five previously captured at Nirvana, a site almost as dark (grey LP) but looking south towards large cities. The image from the less dark site can be compared: a little less detail, and less dynamic range with more noise. The Nirvana frames were captured with the camera oriented 90 degrees wrt the Verendrye frames - a good way to sigma clip away equipment-generated noise and star spikes, but the final image consists only of the intersection area, so the nebula is more tightly framed here than I might like.
I also photographed M30 and the Sculptor galaxy that night. They are at similar altitude, less than 20 degrees, and their images are clearly red-tinted because they lay so close to the horizon. It seems likely this Helix image suffers from the same problem.
Verendrye airstrip, September 10, 2010, 10:55 PM - 1:00 AM; T=+6 C, seeing very good. 7x15 min + 5x15 min at Nirvana, Orion Starshoot on 120mm refractor; no filters; autoguided.