M-101 (NGC-5457) a face-on Type Sc spiral galaxy located in Ursa Major, just NE of the last star in the handle of the "dipper". It was discovered by Pierre Mechain in 1781 and added to Charles Messier's catalog the same year as number 101. The exact distance to M-101 has been disputed for many years. Alan Sandage and Gustav Tammann spent 10 years with the Palomar 200" telescope studying faint Cepheid-type variable stars in M-101 and came up with a distance of 15 million light years. New data gathered by astronomers using the Hubble Space Telescope have revised this distance estimate as closer to 21 million light years from Earth. M-101 is over 170,000 light years in diameter and has a mass of over 16 billion suns, making it the largest galaxy in our Local Group.
This image, acquired on June 5, 2018, is a 1 hour 12 minute integration of 6 minute exposures through the Celestron C-11 at f2, using the HyperStar III imaging system and the Starlight Express SXVR-H694C color CCD camera, operating at -10 degrees below ambient temperature and binned 1 X 1. Guided, captured and combined using Maxim DL5 Pro. Post processed using PhotoShopCS2, Gradient XTerminator, StarShrink, Carboni's Astro Tools and NoiseWare.