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ABELL 21 (AKA PK 205 + 14.5; MEDUSA NEBULA)

Planetary Nebula in Gemini

 (ra: 07:29.02 / dec 13:14)

 

 

 

 

February 2011, Complejo La Aldea in Villa de Merlo

San Luis, Argentina

 

 


 

DATA

TYPE: Planetary Nebula

APPARENT MAGNITUDE: 16

SIZE: 10 x 6 arc minutes

DISTANCE: 1500 light years

   

OBJECT DESCRIPTION AND IMAGE SESSION

A large planetary nebula in the constellation of Gemini on the Canis Minor border. It also known as Abell 21 and Sharpless 274. It was originally discovered in 1955 by UCLA astronomer George O. Abell, who classified it as an old planetary nebula.[4] The braided serpentine filaments of glowing gas suggests the serpent hair of Medusa found in ancient Greek mythology. Until the early 1970s, the Medusa was thought to be a supernova remnant. With the computation of expansion velocities and the thermal character of the radio emission, Soviet astronomers in 1971 concluded that it was most likely a planetary nebula. As the nebula is so big, its surface brightness is very low, with surface magnitudes of between +15.99 and +25 reported. Because of this most websites recommend at least an 8-inch (200 mm) telescope with an [O III] filter to find this object although probably possible to image with smaller apertures (*)

(*) Source Wilkipedia

 

 

IMAGE INFORMATION

SCOPE: Celestron SCT 8" working at f6.3

MOUNT: Sky Watcher HEQ6

SKY CONDITIONS: Transparency and Seeing good

CAMERA: QSI 583 WS -10Cº

FILTERS: Astronomik Type 2, Ha 6 nm

EXPOSURES: LHaRGB (20,30,20,20,20) RGB binned 2x2

GUIDING: William Optics ZenithStar 66 f6. Starlight Xpress Lodestar Camera. AA 3.71 Control Camera Plug-in

PROCESSING: No darks, nor flats, nor offsets. Images Plus (Sigma Median Combination) Robert Vanderbei Richardson Lucy Deconvolution; NASA Photoshop Fits Liberator, Photoshop CS