Galaxy
Pinwheel Galaxy (M101)
In Ursa Major (UMa) • Magnitude 7.9 • 29 arcminutes
Open the free AstroPlanner with Pinwheel Galaxy pre-selected, scored against your telescope, location, and the live cloud forecast.
A nearly perfectly face-on spiral about 21 million light-years away, with enormous sprawling arms and a total diameter of roughly 170,000 light-years — significantly larger than the Milky Way. In 2011 a Type Ia supernova (SN 2011fe) exploded in M101, one of the brightest and closest supernovae in decades, briefly visible through binoculars.
Pinwheel Galaxy at a glance
| Catalog IDs | M101, N 5457 |
| Type | Galaxy |
| Constellation | Ursa Major (UMa) |
| Right ascension | 14h 03m 11s |
| Declination | +54° 21' 00" |
| Apparent magnitude | 7.86 |
| Surface brightness | 14.9 mag/arcsec² |
| Angular size | 28.8 × 26.9 arcmin |
| Max altitude at 45°N | 81° |
| Best imaging months | Jan, Feb, Mar |
How to image Pinwheel Galaxy
Pinwheel Galaxy sits in the constellation Ursa Major at right ascension 14h 03m 11s and declination +54° 21' 00". To frame and integrate it well, AstroPlanner will compute the optimal moonless window for tonight from your location, the field-of-view fit against your sensor and focal length, the suggested total integration time given your aperture and sky Bortle class, and a cloud-aware schedule that drops it from the plan if your nearest cloud forecast spike overlaps the best altitude window. As a galaxy, Pinwheel Galaxy needs the darkest skies you can find: surface brightness, not just apparent magnitude, drives whether it will lift out of the gradient.