M 21 (NGC 6531)
M 21 (NGC 6531) is an open cluster in the constellation Sagittarius, magnitude 6.5, 13′ across.
A compact, young open cluster just northeast of the Trifid Nebula (M20); the two share a low-power field.
When and where to see it
It is best placed in the evening sky around July, when it crosses the meridian at about 10 pm local time (around midnight in June). It can be seen from everywhere south of 68°N and never sets south of 68°S.
At its highest it stands 18° up from 50°N, 33° up from 35°N, 68° up from the equator, 77° up from 35°S.
Facts
- Type
- Open cluster
- Constellation
- Sagittarius
- Designations
- NGC 6531, Webb's Cross Cluster
- Magnitude
- 6.5
- Apparent size
- 13′
- Position
- RA 18h 4.2m, Dec −22° 29′ (J2000)
Open AstroPilot to see when M 21 (NGC 6531) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.