Abell 39, PN G047.0+42.4 (Spring 2013)

 Full resolution image here.

This is Abell 39, a planetary nebula in the constellation Hercules.  The nebula fascinates because it is almost perfectly spherical.  Like all planetary nebulae, Abell 39 is the remains of a dying star.  The dying star is the central star within the nebula.  The sphere glows primarily in the light of oxygen excited by the radiation from the central star.  Here is a close crop of the nebula:

 Telescope: Astro-Tech AT111EDT and William Optics AFR-IV (eff. at f/5.6)
Camera and Exposure: SXVF-H9 (OIII: 31x1200" and combined in RGB with R (14x300"), G (15x300" + 90% OIII), B (15x300" + 20% OIII)), Alnitak Flat-man flats
Filter: Astronomik RGB & OIII
Guiding: SX Lodestar and SX OAG
Mount: Takahashi NJP
Software: Nebulosity, Maxim DL, Photoshop CS3 (one Carboni action), Registar
Location: The Woodlands, TX