The Pacman Nebula (NGC281) in Cassiopeia, at a distance of about 10,000 light-years, is so named because it bears a superficial resemblance (in short exposures) to the mouthy figure in the video game of the same name. True color images of the Pacman do not typically show much interesting color differentiation, but narrowband imaging really brings out the best in this emission nebula, in my humble opinion! The interior glows cyan-blue in Oxygen III light illuminated by star cluster IC1590. The margins and pillars exhibit a variety of reds, oranges and greens in sulfur II (red) and hydrogen-alpha (green) light mapped with the Hubble palette. This image is a 27 hour total narrowband exposure obtained (primarily robotically) using the 14.5-inch Mt. Binky RCOS and U16M Apogee camera at -30C. It is a L(H-a) R(SII) G(Ha) B(OIII). RGB stars are added by layering from a separate short RGB exposure with the same set-up in an attempt to replace the many magenta stars inherent in Hubble palette images. I definitely need to improve in this area! The best narrowband images of the Pacman I know of are Don Goldman’s and Brigham Young University’s processed by Rob Gendler (link below).
http://www.robgendlerastropics.com/NGC281text.html – info about Pacman
http://www.robgendlerastropics.com/NGC281-BYU.html – Brigham Young Univ. narrowband beaut
CAV Astro-Imager Barry Riu admires PacMan Image on 30″ Dell Ultrasharp