Celestial hemisphere:  Northern  ·  Constellation: Gemini (Gem)
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Abell 21, Torben van Hees
Abell 21
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Abell 21

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Abell 21, Torben van Hees
Abell 21
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Abell 21

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Description

Abell 21 is a planetary nebula in the direction of Gemini at a distance of 1500 light years. It has a size of approx. 4 light years and an age of 8800 years. 

I've always read that this nebula is of low surface brightness. But the Ha was quite brightly visible even in the short exposure broadband RGBs for the stars, and even the OIII signal was revealed. Maybe I my definition of low surface brightness is different than Wikipedia's. Concerning the nickname (Medusa nebula), I can only say: The snake is a lie.

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