The Hercules Globular Cluster, cataloged as Messier 13 and NGC 6205, is one of the finest globular clusters for imaging in the northern sky, glowing at magnitude 5.8 mag with an angular size of 0.6° (33′). Its bright, densely packed core resolves into countless individual stars under moderate focal lengths, so photographers often balance exposure length to avoid burning out the center while still capturing the fainter outer halo. Because the cluster is compact and richly populated, it rewards good seeing and precise focus, making it an ideal target for testing resolution and star sharpness across a field. A moderate telescope on a tracking mount, paired with relatively short sub-exposures, brings out the golden and bluish tones of its stellar population against a dark sky.
Names and Catalog numbers
- Hercules Globular Cluster
- M 13 (Messier 13)
- NGC 6205
- Mel 150 (Melotte 150)
Position and the cosmic neighborhood
The Hercules Globular Cluster sits high in the constellation Hercules at a right ascension of 16h 41m 41.63s and a declination of +36° 27′ 40.8″, placing it well within reach of northern-hemisphere imagers for much of the observing season. Its favorable declination means it climbs nearly overhead from mid-northern latitudes, minimizing atmospheric distortion and offering long imaging windows through the shorter nights of summer. Located roughly 26,100 light-years from Earth and spanning some 250 light-years across, this ancient stellar swarm stands out against a relatively sparse surrounding star field, which helps frame it cleanly and simplifies background gradient control during processing.
Nice to Know
- At magnitude 5.8 mag, the Hercules Globular Cluster is bright enough to be a rewarding target even for modest imaging setups and short total integration times.
- The cluster measures 250 light-years across yet appears only 0.6° (33′) wide in the sky, a compactness that makes its resolved core especially photogenic.
- It carries several catalog designations, including Messier 13, NGC 6205, and Melotte 150, reflecting its long history as a celebrated deep-sky object.
- Its radial velocity of -244.4 km/s means the cluster is approaching us, corresponding to a slight blueshift of z = -0.000814899.
Brightness, distance and size
The object has an apparent magnitude of 5.8 mag, it lies about 26,100 light-years from Earth and spans roughly 250 light-years across. On the sky it appears about 0.6° (33′) in size.
