Abell 21 or PK 205+14.1 or Sharpless 2-274 or the Medusa Nebula (2-7-2011)

This planetary nebula is about 1,500 light years away in the constellation Gemini. It's older than many planetaries and is colliding with interstellar matter. That gives it the dramatic look. My favorite image of this critter is Bob Franke's.

This image is 36x7' (4.2 hours) through an Astronomik 12nm Ha [+NII] filter with the Atik 16 and Orion 120mm + WO 0.8x II ff/fr = f/4 achromat.

Here's a colorized version.