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Jon Greif

Location of Photo:

La Jolla, CA, USA

Date/Time of photo:

June 11, 2022, at 11 pm PDT


Takahashi FSQ-85ED with 1.01 Flattener, ZWO ASI533MC Pro imaging camera, Optolong L-Pro filter, ZWO 30 mm guide scope, ZWO ASI290MM mini guide camera, Rainbow Astro RST-135 mount, ZWO ASIAIR Plus controller and capture software, and Pixinsight 1.8.9 processing software on a Macbook Pro


The Pinwheel Galaxy (also known as Messier 101 or M101) is a face-on spiral galaxy 21 million light-years from Earth, in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion 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 between 100,000 and 120,000 light-years. M101 has around a trillion stars. 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. This image from last night represents just 70 minutes of exposure time (fourteen 300 second exposures), between night fall and when the clouds rolled in. The only good part of an early cloud cover is that we got to sleep early!