M 71 Deep sky · Globular cluster in Sagitta · M 71 · NGC 6838
Angelfish Cluster
A loose cluster in Sagitta that astronomers argued over for decades: an open cluster or a globular? It is a sparse globular.
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- Type
- Globular cluster
- Designations
- M 71 · NGC 6838
- Constellation
- Sagitta
- Apparent magnitude
- 6.1
- Apparent size
- 7′
- Position (J2000)
- RA 19h 54m · Dec +18° 47′
The full Moon, about 31′ across, is 4.3 times as wide. The Sun comes no nearer to it than 39°, around late January, so it is never lost in the Sun’s glare, which reaches about 15° out.
When to see it
On the night of Sun 18 Jul 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 17:28 | 01:09 · 57° | 08:49 |
| New York EDT | 17:56 | 01:03 · 68° | 08:11 |
| Singapore GMT+8 | 19:13 | 01:14 · 72° | 07:15 |
| Sydney GMT+10 | 18:59 | 00:05 · 37° | 05:11 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 59° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 36° up in the north.
- When is the best time of year to see it?
- Around mid July, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by mid October it is highest in the early evening, and in mid April not until the hours before dawn.
- How bright is it?
- Magnitude 6.1 in total, but that light is spread over 7′ of sky: on average 19.0 magnitudes per square arcsecond. That is concentrated enough to stand out even against a city’s glow.
- Naked eye, binoculars or telescope?
- The naked eye, from a dark country sky, which shows stars to about magnitude 7.0; from a city, binoculars.
Look for
It sits halfway along the shaft of Sagitta, the little arrow above Altair. A telescope shows a scattered glow.
Look for
From 50° north it climbs to 59°; from 35° north it climbs to 74°; from the equator it climbs to 71°; from 35° south it climbs to 36°.
Look for
Magnitude 6.1 against the faintest star each can show: the eye under a city sky, 4.5 (1.6 short); the eye under a dark country sky, 7.0 (0.9 to spare); 50 mm binoculars under that dark sky, 11.0 (4.9 to spare); a 100 mm telescope there, 12.5 (6.4 to spare). Those limits are for a point of light; its light is spread over its whole size, so it needs some of that margin in hand. Through 7×50 binoculars, whose field is about 7.1° across, it spans 2% of the field’s width; through a 100 mm telescope at 50×, a field about 1° across, it spans 12% of the field’s width.