M21
open cluster · Sagittarius · 5.9ᵐ
A Messier catalogue object — open cluster in Sagittarius.
Notable facts
About 1/2 the apparent diameter of the Moon.
In brief
Which constellation is M21 in?
M21 lies in Sagittarius.
Is M21 visible to the naked eye?
5.9ᵐ — visible to the naked eye (under dark skies).
When is the best time to observe M21?
Best observed in June.
Data
- RA / Dec (J2000)
- 18h 05m · −22° 30′
- Type
- open cluster
- Constellation
- Sagittarius
- How to observe
- 5.9ᵐ — visible to the naked eye (under dark skies)
- Angular size
- 13′
- Designation
- M21 · NGC 6531
Observing tip
Best in binoculars or a telescope at low power, so the whole cluster fits in the field of view.
Altitude above the horizon by latitude
| Latitude | Maximum altitude | Rise azimuth |
|---|---|---|
| +60° | 8° | 140° |
| +55° | 13° | 132° |
| +45° | 23° | 123° |
| +30° | 38° | 116° |
| 0° | 68° | 113° |
| −35° | 78° | 118° |
Geometric altitude at upper culmination, atmospheric refraction not included. Positive latitudes are in the northern hemisphere.
Culmination time by month
| Month | Culmination |
|---|---|
| January | 10:19 |
| February | 08:12 |
| March | 06:26 |
| April | 04:33 |
| May | 02:39 |
| June | 00:33 |
| July | 22:29 |
| August | 20:28 |
| September | 18:35 |
| October | 16:46 |
| November | 14:45 |
| December | 12:37 |
Upper culmination in local solar time — no time-zone or daylight-saving correction applied.