This is a case where the name of a nebula is pretty obvious. The propeller is an emission nebula in the constellation Cygnus. It is one of the more mysterious objects of this type. In particular, we don’t have a clue how it became this shape!
This is a narrowband image, captured at Wa-
Scope: AP Starfire 142 at f/7.5
Mount: AP Mach1
Camera: QSI 583wsg at –