Open cluster
M41 (M41)
In Canis Major (CMa) • Magnitude 4.5 • 38 arcminutes
Open the free AstroPlanner with M41 pre-selected, scored against your telescope, location, and the live cloud forecast.
A bright open cluster in Canis Major noted by Aristotle as early as 325 BC — over 2,000 years before Messier catalogued it. The reddish star near its centre is a red giant roughly 700 times larger than the Sun; if placed in our solar system, it would engulf everything out to the orbit of Mars.
M41 at a glance
| Catalog IDs | M41, N 2287 |
| Type | Open cluster |
| Constellation | Canis Major (CMa) |
| Right ascension | 06h 46m 01s |
| Declination | -20° 45' 00" |
| Apparent magnitude | 4.50 |
| Angular size | 38.0 × 38.0 arcmin |
| Max altitude at 45°N | 24° |
| Best imaging months | Sep, Oct, Nov |
How to image M41
M41 sits in the constellation Canis Major at right ascension 06h 46m 01s and declination -20° 45' 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.