IC 5076 (also V2140 Cygni) is a reflection nebula located in the constellation of Cygnus.
The nebula is related to the star HD 199478, a blue supergiant of spectral class B8Iae with strong emission lines peculiar to a Be star; its apparent magnitude is equal to +5.73 , and being a variable star (catalogued as V2140 Cygni) shows brightness variations of the order of 0.1 magnitudes. Its distance is about 5700 light years away, and in the same galactic region of the nebulous Cygnus X complex, together with the nearby open cluster NGC 6991, visible just to the south of the nebula.
The nebula, and nearby open cluster was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Windsor Road in Slough, Berkshire, on the 27th September 1788.
NGC 6991 is an open star cluster located about 5700 light years away in the constellation Cygnus. However, it is actually two separate clusters discovered by John Herschel and William Herschel and mistakenly listed together as NGC 6991.
The first cluster (IC 5076, centred around the star HD 199478) was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Windsor Road in Slough, Berkshire, on the 27th September 1788.
Right Ascension 20h 55m 39.0s, Declination +47° 26' 54"
The second fainter cluster nearby was discovered by British astronomer John Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflecting telescope at Windsor Road in Slough, Berkshire, on the 14th September 1829.
Right Ascension 20h 54m 56.4s, Declination +47° 18' 38"
