Eagle Nebula

M16, aka NGC 6611, aka the Eagle Nebula, is in Serpens, near the borders between Serpens, Scutum, and Sagittarius, and about 8000 lightyears distant.

This bicolor image was obtained by processing 4 hours of Ha data and 4 hours of OIII data in 2 different ways. First, a RGB was produced, using R=Ha, G=OIII, and B=OIII. This is legitimate, since the "color" of the OIII emission line at 501nm is considered "teal" -- right between the blue and green portions of the spectrum. Then a second image was produced using Steve Cannistra's modified bicolor technique, which synthesizes a green channel from the other 2. Finally, the 2 versions were combined in Photoshop with 50/50 weighting.