The Medusa Nebula is 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.
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 (WIKI)

Imaged with the Boren-Simon 8" F/2.8 POWERNEWT Astrograph.
SBIG ST8300M camera with SBIG Filterwheel with BAADER LRGB filters.
EQ6 PRO mount with PHD guiding.
25x1 min for luminance bin x1
9 min per RGB channel bin X2
Total of 52 minutes.
Imaged from the NEGEV desert in ISRAEL on March 31st 2011