Abell21 (PK 205 +14.1) is a pretty large (12 arc-minutes) Planetary Nebula,situated in the constellation of Gemini.Its real distance is about 1500 light-years.It was detected in 1955 by George Abell and Hugh M.Johnson.
For its special looking filamentary structure it is nick-named as Medusa Nebula,resembling her wounderfull hairs.
Abell 21 earlier was discussed to be a SNR,but Soviet astronomers reveilled in the 1970ies its real nature by measuring the expansion velocities and the thermal character of the radio emissions.
position (epoch 2000):
RA.: 07h 29m 02,7s
Decl.: +13° 14′ 48″
LRGBHaOIII image from:
a total of 17.3 hours
80cm f/7 AstroOptik Keller corrected cassegrain FLI Proline 16803 Astrodon LRGB GenII filters
Prompt 7 CTIO/UNC Chile,remote controlled
image processing: Bernd Flach-Wilken
here you have a picture of the Medula Nebula in a 94% FOV of the used FLI-camera.
For full resolution click HERE.
HERE is a link to a very detailed image,taken with one of the VLT-(ESO)-telescopes.