Open cluster in Perseus
M34
A wide, loose scattering that wants low power and a wide field, and is spoiled by anything else. At 200 million years it is middle-aged: the heavy stars have already gone, and the remainder will drift apart in time.
About a hundred stars, of which a good number are doubles, and it lies close enough that its members can be picked out individually rather than blurring into a haze. It is drifting through space alongside the Pleiades and the Hyades on a roughly shared course, which suggests all three condensed out of the same general stretch of gas.
- Catalogue
- M34
- Type
- Open cluster
- Constellation
- Perseus
- Distance
- 1,500 light-years
- Apparent magnitude
- 5.5
- Surface brightness
- 21.8 mag/□″
- Apparent size
- 35′
- Right ascension
- 2h 42m
- Declination
- +42.78°
- Found by
- Giovanni Batista Hodierna, before 1654
Magnitude 5.5 for the cluster as a whole, though that is a sum rather than a thing you see: what reaches you is a scatter of separate stars, and whether you catch it depends on how bright the brightest of them are. Why surface brightness is the number that matters.
Could you see it?
Straightforward with the naked eye from Bortle 5 or darker; with 10×50 binoculars from Bortle 9.
| Sky | Eye | 10×50 | 80mm | 130mm | 200mm |
|---|---|---|---|---|---|
| Bortle 1 21.9 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 2 21.7 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 3 21.4 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 4 20.9 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 5 20.3 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 6 19.3 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 7 18.6 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 8 18.1 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 9 17.8 mag/□″ | No | Easy | Easy | Easy | Easy |
At the eyepiece
Wide, bright and best in binoculars or the lowest power a telescope can manage. Around eighty stars in loose pairs and chains, several of them doubles worth splitting. This is a cluster to look at rather than study, and it is over quickly.
When, and from where
Highest in the middle of the night in October. Well placed for the northern hemisphere and overhead for anyone near 43°N. South of 47°S it stays below the horizon.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 73° | Never sets |
| 51°N London, Calgary | 82° | Never sets |
| 40°N New York, Madrid | 87° | |
| 30°N Cairo, Houston | 77° | |
| 0°N the equator | 47° | |
| 33°S Sydney, Cape Town | 14° | Low — in the murk |
Nearby in the sky
The whole catalogue →Nothing else in the catalogue is especially close; the nearest is 13° apart, which is a separate trip rather than a nudge of the tube. Everything below is measured from M34 itself, not from the middle of Perseus.
- M76 Little Dumbbell 13° apart Perseus · magnitude 10.1 · binoculars from Bortle 4 or darker
- M33 Triangulum Galaxy 18° apart Triangulum · magnitude 5.7 · binoculars from Bortle 3 or darker
- M103 Open cluster 21° apart Cassiopeia · magnitude 7.4 · binoculars from Bortle 9 or darker
- M31 Andromeda Galaxy 22° apart Andromeda · magnitude 3.4 · binoculars from Bortle 4 or darker
One of 110. Positions J2000; the sky is the final authority.