Globular cluster
M3 (M3)
In Canes Venatici (CVn) • Magnitude 6.2 • 18 arcminutes
Open the free AstroPlanner with M3 pre-selected, scored against your telescope, location, and the live cloud forecast.
A glittering ball of roughly 500,000 stars and one of the finest globular clusters in the northern sky. It holds an extraordinary record: over 270 variable stars — stars that rhythmically pulse in brightness — more than almost any other known globular cluster.
M3 at a glance
| Catalog IDs | M3, N 5272 |
| Type | Globular cluster |
| Constellation | Canes Venatici (CVn) |
| Right ascension | 13h 42m 11s |
| Declination | +28° 22' 48" |
| Apparent magnitude | 6.20 |
| Surface brightness | 11.6 mag/arcsec² |
| Angular size | 18.0 × 18.0 arcmin |
| Max altitude at 45°N | 73° |
| Best imaging months | Jan, Feb, Mar |
How to image M3
M3 sits in the constellation Canes Venatici at right ascension 13h 42m 11s and declination +28° 22' 48". 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.