Messier 71, also catalogued as NGC 6838, is a compact globular cluster nestled within the small constellation Sagitta. Spanning about 7.2′ on the sky, it makes a rewarding target for astrophotographers working with medium to long focal lengths who want to resolve its loose swarm of stars. Because it sits against the dense backdrop of the summer Milky Way, wide-field captures place this cluster amid a glittering star field that adds depth and context to the frame. Its modest size means that careful focus, good seeing, and sufficient integration time are key to teasing out the cluster’s individual member stars without blowing out its bright core.
Names and Catalog numbers
- M 71 (Messier 71)
- NGC 6838
- Mel 226 (Melotte 226)
Position and the cosmic neighborhood
Messier 71 lies at right ascension 19h 53m 46s and declination +18° 46′ 45″, embedded in the tiny but distinctive constellation Sagitta, the Arrow. This region of sky cuts straight through the rich star clouds of the summer Milky Way, so the cluster shares its frame with countless field stars and faint nebulosity. The compact arrow shape of Sagitta makes for an easy star-hop to the cluster, and its placement between the brighter constellations Aquila and Cygnus gives wide-field imagers plenty of surrounding texture to compose around. With a physical diameter of about 27 light-years, Messier 71 appears as a gently concentrated glow that rewards patient framing within this crowded galactic neighborhood.
Nice to Know
- Messier 71 was long debated as either a dense open cluster or a loose globular cluster, giving it an unusually transitional appearance that makes it a distinctive imaging subject.
- The cluster sits about 13,000 light-years from Earth, yet its relatively loose concentration allows individual member stars to be resolved with moderate apertures.
- Its small apparent size of 7.2′ rewards longer focal lengths, while its setting in the summer Milky Way also makes it a striking wide-field target.
- Carrying several designations including M 71, NGC 6838, and Mel 226, the cluster shows a radial velocity of -22.5 km/s, indicating it is moving toward us.
Brightness, distance and size
It lies about 13,000 light-years from Earth and spans roughly 27 light-years across. On the sky it appears about 7.2′ in size.
