Object: Constellation: Coordinates: Size: Brightness:
Messier 101
(NGC 5457)
UMa 14h03m / +54°21' 28.8' x 26.9' 7.5mag

The spiral galaxy Messier 101 (NGC 5457, Pinwheel galaxy) in the constellation Ursa Major on April 7 / 8, 2018 and on May 4 / 5, 2016. 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).

Seventy-four exposures of 3 minutes at ISO 800 were stacked with no dark frame subtraction with Deep Sky Stacker (resulting in a 3 h 47 min exposure) and further processed in Photoshop.
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).

Search chart for Messier 101. Map © 2018 "The Mag-7 Star Atlas Project", www.siaris.net. Map is modified.
The Mag-7 Star Atlas Project map can be downloaded here .