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Sharpless 112, Sharpless 115 and Abell 71

Sh2-112, Sh2-115, Abell 71

Sh2-112 (near the bottom) and Sh2-115 (upper part of the image) are faint emission nebulae catalogued by S. Sharpless in 1959. They are located in Cygnus, just 1 and 2 degrees northwest of Deneb, the brightest star of this constellation. The brightest parts of the Sharpless nebulae can be glimpsed visually, but it takes a dark sky and a decent rich-field telescope.

Abell 71 is the designation of the small round patch of emission nebulosity near the upper edge of the photo, it actually shows two extensions or "arms". Originally it was classified as one of four planetary nebulae in Cygnus by G. Abell in 1955. Subsequent studies question this because it emits almost no greenish [OIII] light characteristic of a planetary nebula, so it could simply be another HII region, although it is still cataloged as PN in most databases.

The nebula emits all of its light in isolated emission lines. The most prominent of these are the lines Hα, [OIII] and [SII], which were recorded exclusively to capture the image shown above. This is a "natural color" composition that is mixed so that the resulting colors come close to the visible spectrum of the human eye. The following mixture was used:

Central Cygnus Region, zoom lens photograph.
Sharpless 112, Sharpless 115 and Abell 71 in Hα, which is part of this image.
Sharpless 115 and vdB 134, Wright-Newtonian photograph.


Exposure Data


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© 2019 Walter Koprolin