M 73 Deep sky · Open cluster in Aquarius · M 73 · NGC 6994
M 73
Just four faint stars in a Y shape in Aquarius: the catalogue’s puzzle, and probably no cluster at all, only a chance line-up.
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- Type
- Open cluster
- Designations
- M 73 · NGC 6994
- Constellation
- Aquarius
- Apparent magnitude
- 8.9
- Apparent size
- 3′
- Position (J2000)
- RA 20h 59m · Dec −12° 38′
The full Moon, about 31′ across, is 11 times as wide. The Sun passes 4° from it around early February, and for about 29 days of the year it sits within 15° of the Sun, lost in its glare.
When to see it
On the night of Tue 3 Aug 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 20:17 | 01:11 · 26° | 06:05 |
| New York EDT | 19:51 | 01:06 · 37° | 06:21 |
| Singapore GMT+8 | 19:19 | 01:16 · 76° | 07:14 |
| Sydney GMT+10 | 17:34 | 00:07 · 69° | 06:41 |
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 early August, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by early November it is highest in the early evening, and in early May not until the hours before dawn.
- Naked eye, binoculars or telescope?
- Binoculars. At magnitude 8.9 it is past the eye, but a 50 mm pair under a dark sky reaches about magnitude 11.0.
Science
Measurements of its stars’ distances and motions show they are not travelling together, so it is an asterism — a pattern, not a family.
History
Messier saw a faint haze around the stars and listed them; better telescopes found nothing there.
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 8.9 against the faintest star each can show: the eye under a city sky, 4.5 (4.4 short); the eye under a dark country sky, 7.0 (1.9 short); 50 mm binoculars under that dark sky, 11.0 (2.1 to spare); a 100 mm telescope there, 12.5 (3.6 to spare). Through 7×50 binoculars, whose field is about 7.1° across, it is a speck under 1% of the field’s width; through a 100 mm telescope at 50×, a field about 1° across, it spans 5% of the field’s width.