Globular cluster
M4 (M4)
In Scorpius (Sco) • Magnitude 5.9 • 36 arcminutes
Open the free AstroPlanner with M4 pre-selected, scored against your telescope, location, and the live cloud forecast.
The closest globular cluster to Earth at just 7,200 light-years, making it appear larger and more loosely packed than more distant cousins. Astronomers found some of the oldest known white dwarf stars inside it — the cooling embers of ancient suns around 13 billion years old, essentially the universe's very first generation of stars.
M4 at a glance
| Catalog IDs | M4, N 6121 |
| Type | Globular cluster |
| Constellation | Scorpius (Sco) |
| Right ascension | 16h 23m 35s |
| Declination | -26° 31' 48" |
| Apparent magnitude | 5.90 |
| Surface brightness | 12.5 mag/arcsec² |
| Angular size | 36.0 × 36.0 arcmin |
| Max altitude at 45°N | 18° |
| Best imaging months | Feb, Mar, Apr |
How to image M4
M4 sits in the constellation Scorpius at right ascension 16h 23m 35s and declination -26° 31' 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.