Globular cluster
M15 (M15)
In Pegasus (Peg) • Magnitude 6.4 • 18 arcminutes
Open the free AstroPlanner with M15 pre-selected, scored against your telescope, location, and the live cloud forecast.
One of the densest globular clusters known — its centre has undergone "core collapse," a catastrophic runaway gravitational compression of the inner stars over billions of years. It is also one of only a handful of globulars known to contain a planetary nebula (Pease 1) right inside it, making it doubly remarkable.
M15 at a glance
| Catalog IDs | M15, N 7078 |
| Type | Globular cluster |
| Constellation | Pegasus (Peg) |
| Right ascension | 21h 30m 00s |
| Declination | +12° 10' 12" |
| Apparent magnitude | 6.40 |
| Surface brightness | 12.0 mag/arcsec² |
| Angular size | 18.0 × 18.0 arcmin |
| Max altitude at 45°N | 57° |
| Best imaging months | May, Jun, Jul |
How to image M15
M15 sits in the constellation Pegasus at right ascension 21h 30m 00s and declination +12° 10' 12". 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.