Crescent Nebula (NGC 6888) in Cygnus
NGC 6888 (Caldwell 27) is one of the more intriguing objects in our galaxy as it is located around HD 192163, a 7.5‑mag Wolf-Rayet star. It has long been believed that this extremly luminous sun is heating a part of it outer atmosphere which has a diameter of roughly 20 lightyears. The Crescent Nebula spans an area of about 18x13 arc minutes in the constallation of Cygnus, roughly 4700 lightyears away.
[description from O’Meara]