Messier 92, also cataloged as NGC 6341, is a densely packed globular cluster in Hercules that shines at an apparent magnitude of 6.52, making it a rewarding target for astrophotographers even under moderate skies. Spanning roughly 11′ across the sky, it presents a compact but well-resolved core that benefits from moderate to long focal lengths to tease out its swarm of individual stars. Its high surface brightness of about 20.4 mag/arcsec² means shorter subexposures can preserve the bright center while longer integrations bring out the fainter outer halo stars. Careful attention to focus and seeing conditions pays off here, as the tightly concentrated core rewards sharp optics and precise tracking with a jewel-like resolution of thousands of stars.
Names and Catalog numbers
- M 92 (Messier 92)
- NGC 6341
- Mel 168 (Melotte 168)
Position and the cosmic neighborhood
Messier 92 (NGC 6341) sits high in the northern sky within the constellation Hercules, at a declination of about +43°, which makes it a favorable, near-overhead target for observers and imagers across the northern hemisphere. Positioned at right ascension 17h 17m, it lies in the same region of sky as its more famous neighbor Messier 13, and the two globulars make an appealing pair to frame across an imaging session in the same part of the constellation. Its northerly placement keeps it well clear of the horizon murk for much of the year, offering long, steady windows for deep-sky photography.
Nice to Know
- Messier 92 lies about 29,100 light-years from Earth, yet still glows at a readily accessible magnitude 6.52.
- The cluster spans roughly 95 light-years in physical diameter, which corresponds to an apparent angular size of about 11′.
- It carries several catalog designations, including M 92, NGC 6341, and Mel 168.
- M 92 is approaching us with a radial velocity of about -120.7 km/s, reflected in its slight blueshift of z = -0.000402531.
Brightness, distance and size
The object has an apparent magnitude of 6.5 mag, it lies about 29,100 light-years from Earth and spans roughly 95 light-years across. On the sky it appears about 11′ in size.
