M 10 Deep sky · Globular cluster in Ophiuchus · M 10 · NGC 6254
M 10
One half of a matched pair of globular clusters in the middle of Ophiuchus — the brighter, more concentrated one.
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- Type
- Globular cluster
- Designations
- M 10 · NGC 6254
- Constellation
- Ophiuchus
- Apparent magnitude
- 6.4
- Apparent size
- 20′
- Position (J2000)
- RA 16h 57m · Dec −04° 06′
The full Moon, about 31′ across, is 1.6 times as wide. The Sun comes no nearer to it than 18°, around early December, so it is never lost in the Sun’s glare, which reaches about 15° out.
When to see it
On the night of Thu 3 Jun 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 19:32 | 01:10 · 34° | 06:48 |
| New York EDT | 19:20 | 01:04 · 45° | 06:49 |
| Singapore GMT+8 | 19:16 | 01:15 · 85° | 07:14 |
| Sydney GMT+10 | 17:56 | 00:06 · 60° | 06:16 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 36° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 59° up in the north.
- When is the best time of year to see it?
- Around early June, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by early September it is highest in the early evening, and in early March not until the hours before dawn.
- How bright is it?
- Magnitude 6.4 in total, but that light is spread over 20′ of sky: on average 21.5 magnitudes per square arcsecond. Against a dark country sky that average stands out; a city’s glow drowns all but its brightest parts.
- 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
Binoculars can hold it and its neighbour M 12 in the same sweep. M 10 looks a little brighter and tighter at the centre.
Look for
From 50° north it climbs to 36°; from 35° north it climbs to 51°; from the equator it climbs to 86°; from 35° south it climbs to 59°.
Look for
Magnitude 6.4 against the faintest star each can show: the eye under a city sky, 4.5 (1.9 short); the eye under a dark country sky, 7.0 (0.6 to spare); 50 mm binoculars under that dark sky, 11.0 (4.6 to spare); a 100 mm telescope there, 12.5 (6.1 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 5% of the field’s width; through a 100 mm telescope at 50×, a field about 1° across, it spans 33% of the field’s width.