I prefer to call this one the Croissant Nebula, but this is the Crescent Nebula, an emission nebula 5000 light-years away in the constellation Cygnus. It was formed by a shockwave collision caused by the Wolf-Rayet star WR136. A long time ago when the star was a red giant, it was releasing slower stellar wind than it is now. The new faster stellar winds impacted the older ones creating a shock front that ionized the surrounding gasses.
This image uses multiple nights of exposure, captured from the Eastern Sierra Mountains in California. The location provides peculiarly stable seeing conditions, allowing for great details to be shown. This is probably one of the most detailed images ever captured of the nebula, and you can really tell in the print!
The telescope used was a 16” RCOS with a ZWO ASI6200MM, on a paramount ME.