The spiral galaxy Messier 101 (NGC 5457, Pinwheel galaxy) in the constellation Ursa Major
on May 4 / 5, 2016, on April 7 / 8, 2018, and on April 16 / 17, 2020. Messier 101 has a diameter of 170'000 light years and is approximately 22 million light-years from
Earth. The galaxy was discovered by French astronomier Pierre Méchain in 1781 (source: Wikipedia).
One hundred and seven exposures of 3 minutes at ISO 800 were stacked with no dark frame subtraction with Deep Sky Stacker (resulting in a
5 h 26 min exposure) and further processed in Photoshop.
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Equipment: Canon EOS 450D Baader modified camera, TeleVue Paracorr Type II coma corrector,
16" f/4.5 "Ninja" dobsonian telescope riding on a dual-axis Tom Osypowski equatorial platform,
Lacerta MGEN autoguider, Lacerta off axis system (field of view comparison:
image of the moon with the same equipment).
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