From WikiPedia: Thor's Helmet is an emission nebula in the constellation Canis Major (The Great Dog). The nebula is approximately 15,000 light-years away and 30 light-years in size. The central star is the Wolf-Rayet star HD 56925, an extremely hot giant thought to be in a brief, pre-supernova stage of evolution. It is similar in nature to the Bubble Nebula, interactions with a nearby large molecular cloud are thought to have contributed to the more complex shape and curved bow-shock structure of Thor's Helmet. It is also cataloged as Sharpless Sh2-298. The image of Thor's Helmet (NGC 2357) was captured on the evenings of Mar 19 and 20, 2014 from Top of Mississippi Skies (T.O.M.S.) Observatory (lat 34.98°N, lon 88.28°W.) with a TMB-130SS f/7 Apochromatic Refractor on a Celestron CGE-Pro mount and an SBIG STF-8300C camera with an Astronomik CLS-CCD Filter; AutoGuiding was with a Lodestar camera via PHD; focusing was accomplished with a MicroTouch focuser controlled by Rigel Systems nSTEP. 3.6 hrs of data were acquired using ImagesPlus Camera Control v5.75; raw images were calibrated, stacked and processed with IP v5.75.