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M57 / Ring Nebula

Classification: Planetary Nebula M57 / NGC6720
Constellation: Lyra (LYR)
Object Location: Ra 18h 54m 07s Dec +33° 03’07° (current)
Size & Distance: 3.0 x 3.0 Apx 2300 light years.

Date & Location: 05-2/3-2008 Palomar Mountain, CA.
Exposure: Ha= 16 @ 15min. RGB= 3 ea. @ 5min, all (bin 2x2)
Optics: Telescope Engineering Company APO140ED @ f/7 F/L 940mm.
Mount: Astro-Physics 900 GTO / ATS 10x36 pier.
Camera: SBIG-ST10XME / Guided by 2045 SBIG-RGH
Filters: Astrodon 6nm Ha, G2 RGB
Software: MaxImDL 4.56, Photoshop CS

Notes: Sky conditions: Above average seeing, Light wind, Temp 50°
Image Field of view is 35 x 52 arcmin.

The Ring Nebula, M57 or NGC 6720 is a planetary nebula in the northern constellation of Lyra. Such objects are formed when a shell of ionized gas is expelled into the surrounding interstellar medium by a red giant star, which was passing through the last stage in its evolution before becoming a white dwarf.

M57 is 2,300 light-years from Earth. It has a visual magnitude of 8.8v and photographic magnitude of 9.7p. Photographs taken over a period of 50 years show the rate of nebula expansion is roughly 1 arcsecond per century, which corresponds to spectroscopic observations as 20–30 km s−1. M57 is illuminated by a central white dwarf.