Messier 15 dazzles as one of the oldest and densest globular clusters visible in the northern sky. Popular among astrophotographers, its compact core and densely packed stars present an impressive target for telescopes of all sizes, with the striking possibility to capture subtle background nebulosity under optimal conditions. The cluster is home to over 100,000 stars and features a brilliant, tightly concentrated center, making it compelling for long-exposure deep-sky imaging. Notably, it is among the few clusters that contains a visible planetary nebula, adding to its photographic intrigue.
Names and Catalog numbers
- Pegasus Cluster
- Messier 15 (M15)
- NGC 7078
- Melotte 234
Position and the cosmic neighborhood
Messier 15 is located near the border of Pegasus, close to the prominent star Enif (epsilon Pegasi), which acts as a convenient guide for locating the cluster in the sky. In astrophotography star charts, M15 stands out west of the Pegasus constellation’s “Square” asterism, set against a field that can include faint integrated flux nebula (IFN) in deep exposures. The area is largely free of bright foreground stars, which helps when framing the cluster for wide-field and mosaic imaging. In deep images, extremely faint background galaxies can sometimes be revealed in the surrounding field.
Nice to Know
- M15 is one of the densest globular clusters known, having experienced core collapse, resulting in a particularly bright and compact core.
- The cluster hosts the first planetary nebula discovered in any globular cluster, Pease 1, making it a unique target for advanced imaging.
- Astrophotographers have succeeded in revealing faint background nebulosity (IFN) around M15 in long exposures under dark skies.
- It is possible to resolve hundreds of individual stars in M15’s halo with moderate to large telescopes and modern imaging techniques.
Brightnes, distance and size
Messier 15 has an apparent visual magnitude of 6.2, making it accessible to binocular and small telescope observers under dark skies. The cluster resides about 33,600 light years from Earth and spans roughly 175 light years in diameter. Visually, M15 subtends approximately 18 arcminutes across the sky, presenting as a concentrated, round glow in wide-field images. This combination of brightness and size allows for impressive astrophotographs even with short to moderate exposure times, while extended exposures unveil fine details and the faintest outer members of the cluster.
