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Jon Greif

Location of Photo:

Palomar, CA, USA

Date/Time of photo:

May 11, 2021, at 10:00 pm PDT


AT72EDII 72 mm refractor with 4.8F/433 mm focal length, ZWO ASI 533 MC Pro imaging camera, QHY 5Lii guide camera, Rainbow RST-135 mount, Ekos capture software on a Raspberry Pi 4B computer, Pixinsight 1.8.8 processing software on a MacBook Pro computer


The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy 21 million light-years away from Earth in the constellation Ursa Major, near the far end of the handle of the Big Dipper. It was discovered by Pierre Méchain in 1781 and communicated that year to Charles Messier, who verified its position and included it in the Messier Catalogue as one of its final entries. M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 100,000 light-years. M101 has around a trillion stars, twice the number in the Milky Way.