Abell 21 commonly called the Medusa Nebula, is a spectacular nebula with lovely contributions to its detailed stucture from both the Ha and Oiii. It is fairly large extending 10.3 arc minutes. The tiny blue progenitor star is clearly visible in the center. I have imaged it with most of my earlier hardware, and here is a version from my latest configuration.
This moon sized stretch of sky is remarkably devoid of any noticeable galaxies.
My Abell Collection is here:
Abell Planetary NebulaeCurrently 60+, and soon to be complete.
Wikipedia:
The Medusa Nebula is a planetary nebula in the constellation of Gemini. It is also known as Abell 21 and Sharpless 2-274. It was originally discovered in 1955 by University of California, Los Angeles astronomer George O. Abell, who classified it as an old planetary nebula. Until the early 1970s, the nebula 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 large, its surface brightness is very low, with surface magnitudes of between +15.99 and +25 reported.
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