Technical details: Location / Date: Outside of Ramnäs, Västmanland, Sweden / 2015-March Optics: Skywatcher Explorer 190MN Mount: 10 Micron GM1000 HPS (Unguided) Camera: Canon EOS 100D (Modded with Baader ACF filter) Exposure: 39 x 300 seconds, all shot at ISO 3200 (cumulative exposure time is 3 hours and 15 minutes) Processing: Pixinsight and Photoshop   Image details: The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy distanced 21 million light-years away from earth in the constellation Ursa Major, first discovered by Pierre Méchain on March 27, 1781, and communicated to Charles Messier who verified its position for inclusion in the Messier Catalogue as one of its final entries. M101 is a relatively large galaxy compared to the Milky Way. With a diameter of 170,000 light-years it is seventy percent larger than the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses. M101 is noted for its high population of H II regions, many of which are very large and bright. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form. H II regions are ionized by large numbers of extremely bright and hot young stars; those in M101 are capable of creating hot superbubbles. In a 1990 study, 1264 H II regions were cataloged in the galaxy.Three are prominent enough to receive New General Catalogue numbers - NGC 5461, NGC 5462, and NGC 5471 (See anotated version of the image above). M101 is asymmetrical due to the tidal forces from interactions with its companion galaxies. These gravitational interactions compress interstellar hydrogen gas, which then triggers strong star formation activity in M101's spiral arms that can be detected in ultraviolet images.(Information from Wikipedia)