Messier 101 (Ursa Major)
Fig. 1 - Believed to host a trillion stars: The spiral galaxy Messier 101 in Ursa Major, photographed with an 8-inch f/4 Newtonian reflector on a ZWO AM5 mount. The peculiar dwarf galaxy NGC 5474 can be seen on the right of the image. This galaxy is the closest to Messier 101 itself. The gravitational interaction between NGC 5474 and Messier 101 has strongly distorted the former.
| Object name: | Constellation: | Coordinates: | Apparent size: | Visual brightness: |
|---|---|---|---|---|
| Messier 101 (NGC 5457) | Ursa Major | 14h03m / +54°21' | 28.8' x 26.9' | 7.9 mag |
The intermediate spiral galaxy Messier 101 (NGC 5457, Pinwheel Galaxy) in the constellation Ursa Major. Messier 101 is a large galaxy, with a diameter of 170,000 light-years. It is asymmetrical due to the tidal forces from interactions with its companion galaxies. Messier 101 contains a high population of H II regions, around a trillion stars, and is located 21 million light-years from Earth. 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 (source: Wikipedia).
Exposure time: 4h 54min (98x3min) at gain 100 and -10°C, taken on March 3 / 4, 2025. Processing with Astro Pixel Processor (APP) and Photoshop. Darks, flats, and bias were used.
Equipment: Cooled ASI 2600MC Pro camera, TeleVue Paracorr Type II coma corrector, 8" f/4 "ONTC" Newtonian telescope riding on a ZWO AM5 Strain Wave Mount, ZWO OAG-L off axis system, ASI 174MM Mini guide camera, ASIAIR Plus.
Fig. 2 - Search chart for Messier 101. Copyright 2025 'The Mag-7 Star Atlas Project', www.siaris.net.