Planetary nebula NGC 7009 in Aquarius

NGC 7009, a planetary nebula; the Saturn Nebula

Description of NGC 7009 in
The Deep Sky Field Guide to Uranometria 2000:

Quote from Burnham's Celestial Handbook:

......first observed by Sir William Herschel in 1782. It was called by Lord Rosse the "Saturn" Nebula from the extending rays .... which project from the main disc......

The nebula has a rather high surface brightness and appears nearly stellar in small low power telescopes...... ..a strikingly beautiful object in large telescopes, shining with a vivid green fluorescent glow. The flattened central disc measures about 25" X 17" and is enclosed in a larger shell about 30" X 26". There is considerable intricate detail in both rings, and the two projecting rays end in bright condensations about 44" apart...... The central star is an extremely hot bluish dwarf with a continuous spectrum, and a computed temperature of about 55,000K. Strong ultraviolet radiation from the star is the cause of the bright fluorescent glow of the nebulosity and the green tint is due to-the radiation of doubly ionized oxygen.....