This SVX140T image was taken by Juan Marín Otero from within Washington DC, probably some of the worst conditions you can find. It is a bit over 30 hours of narrowband imaging and processed in a modified SHO palette.

The Propeller Nebula, also catalogued as Simeis 57 is an emission nebula that is part of the Cygnus X complex The southern "arm" is catalogued as DWB111 while the northern arm is DWB119. This whole area is very rich in HII regions and has a strong response with an Ha filter. The Cynus X complex lies around 4600 light years from Earth.

More information on this beautiful image is available on Astrobin.