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Abell 21- Medusa Nebula in Gemini

RA= 7 hrs 29 min; Dec = +13 deg 14 min

Date & Site:

Imaged on 12/28 and 12/29/16; Little Blair Valley, CA

Conditions: temps in the low 30's; calm; average-very good seeing


Telescope: DSI RC10c

Guider: SBIG guidehead/Hutech OAG5

Mount: AP 1100 CP3
Camera: ST-10XME; CFW10; Astrodon Ha (3nm); RGB Gen II filters



Exposures: 3 hrs Ha (15 minute subexposures) and 80 minutes each of RGB (10 min subexposures) for total of 7 hrs

It was originally discovered in 1955 by George Abell, who classified it as a planetary nebula. The braided serpentine filaments of glowing gas suggests the serpent hair of Medusa found in ancient Greek Mythology. The nebula spans 4.41 light years.

1,470 light years away

(image reduced to 60% of original size)

FOV = 23 x 15 arc minutes

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