M 25 Deep sky · Open cluster in Sagittarius · M 25 · IC 4725
M 25
A bright open cluster in Sagittarius, within reach of the naked eye, that holds a pulsating Cepheid variable star.
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- Type
- Open cluster
- Designations
- M 25 · IC 4725
- Constellation
- Sagittarius
- Apparent magnitude
- 4.6
- Apparent size
- 26′
- Position (J2000)
- RA 18h 32m · Dec −19° 07′
It is about as wide as the full Moon, which is about 31′ across. The Sun passes 4° from it around late December, and for about 28 days of the year it sits within 15° of the Sun, lost in its glare.
When to see it
On the night of Sun 27 Jun 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 20:54 | 01:10 · 19° | 05:26 |
| New York EDT | 20:15 | 01:05 · 30° | 05:55 |
| Singapore GMT+8 | 19:18 | 01:15 · 70° | 07:12 |
| Sydney GMT+10 | 17:14 | 00:06 · 75° | 06:59 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 21° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 74° up in the north.
- When is the best time of year to see it?
- Around late June, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late September it is highest in the early evening, and in late March not until the hours before dawn.
- 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.
Science
One of its stars, U Sagittarii, is a Cepheid: it brightens and fades on a steady rhythm, and the rhythm gives its true brightness.
Look for
It is north of the Teapot’s lid, and binoculars show it well: a loose scatter of stars on the Milky Way.
Look for
From 50° north it climbs to 21°; from 35° north it climbs to 36°; from the equator it climbs to 71°; from 35° south it climbs to 74°.
Look for
Magnitude 4.6 against the faintest star each can show: the eye under a city sky, 4.5 (0.1 short); the eye under a dark country sky, 7.0 (2.4 to spare); 50 mm binoculars under that dark sky, 11.0 (6.4 to spare); a 100 mm telescope there, 12.5 (7.9 to spare). Through 7×50 binoculars, whose field is about 7.1° across, it spans 6% of the field’s width; through a 100 mm telescope at 50×, a field about 1° across, it spans 43% of the field’s width.
Words used here
Its constellation
Nearby in Sagittarius
- Nebula Lagoon Nebula
- Nebula Trifid Nebula
- Globular cluster Great Sagittarius Cluster
- Nebula Omega Nebula
- Open cluster Black Swan Cluster
- Open cluster Webb's Cross
- Open cluster M 23
- Open cluster Small Sagittarius Star Cloud
- Globular cluster M 28
- Globular cluster M 54
- Globular cluster Specter Cluster
- Globular cluster M 69
- Globular cluster M 70
- Globular cluster M 75