M 107 Deep sky · Globular cluster in Ophiuchus · M 107 · NGC 6171
The Crucifix Cluster
A loose globular cluster in Ophiuchus, and one of the objects added to Messier’s list in the twentieth century.
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- Type
- Globular cluster
- Designations
- M 107 · NGC 6171
- Constellation
- Ophiuchus
- Apparent magnitude
- 8.8
- Apparent size
- 13′
- Position (J2000)
- RA 16h 33m · Dec −13° 03′
The full Moon, about 31′ across, is 2.4 times as wide. The Sun passes 9° from it around late November, and for about 24 days of the year it sits within 15° of the Sun, lost in its glare.
When to see it
On the night of Fri 28 May 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 20:18 | 01:09 · 25° | 06:00 |
| New York EDT | 19:51 | 01:04 · 36° | 06:16 |
| Singapore GMT+8 | 19:16 | 01:14 · 76° | 07:12 |
| Sydney GMT+10 | 17:30 | 00:05 · 69° | 06:40 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 27° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 68° up in the north.
- When is the best time of year to see it?
- Around late May, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late August it is highest in the early evening, and in late February not until the hours before dawn.
- How bright is it?
- Magnitude 8.8 in total, but that light is spread over 13′ of sky: on average 23.0 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?
- Binoculars. At magnitude 8.8 it is past the eye, but a 50 mm pair under a dark sky reaches about magnitude 11.0.
Look for
It lies south of the star Zeta Ophiuchi, in Ophiuchus. A telescope shows a dim glow crossed by darker lanes.
Look for
From 50° north it climbs to 27°; from 35° north it climbs to 42°; from the equator it climbs to 77°; from 35° south it climbs to 68°.
Look for
Magnitude 8.8 against the faintest star each can show: the eye under a city sky, 4.5 (4.3 short); the eye under a dark country sky, 7.0 (1.8 short); 50 mm binoculars under that dark sky, 11.0 (2.2 to spare); a 100 mm telescope there, 12.5 (3.7 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 3% of the field’s width; through a 100 mm telescope at 50×, a field about 1° across, it spans 22% of the field’s width.