Globular cluster
M28 (M28)
In Sagittarius (Sgr) • Magnitude 7.9 • 11 arcminutes
Open the free AstroPlanner with M28 pre-selected, scored against your telescope, location, and the live cloud forecast.
A compact globular cluster in Sagittarius that made history as the first globular cluster found to contain a millisecond pulsar — a neutron star spinning 34 times per second, the recycled remains of a dead star spun up by consuming matter from a companion. Some millisecond pulsars spin over 700 times per second, making them the fastest-rotating solid objects known in the universe.
M28 at a glance
| Catalog IDs | M28, N 6626 |
| Type | Globular cluster |
| Constellation | Sagittarius (Sgr) |
| Right ascension | 18h 24m 29s |
| Declination | -24° 52' 12" |
| Apparent magnitude | 7.86 |
| Surface brightness | 12.3 mag/arcsec² |
| Angular size | 11.0 × 11.0 arcmin |
| Max altitude at 45°N | 20° |
| Best imaging months | Mar, Apr, May |
How to image M28
M28 sits in the constellation Sagittarius at right ascension 18h 24m 29s and declination -24° 52' 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.