Open cluster in Scutum
M26
Modest, and unluckily placed a few degrees from M11, which is far better and gets looked at instead. A curious dark patch near its centre appears to be dust lying between us and the cluster. About ninety million years old and perhaps twenty-two light-years across, with around ninety stars that are actually members.
The dark patch near the centre is the interesting part: it is almost certainly foreground dust, but it is convincingly placed, and it took some work to establish that it was not a hole in the cluster itself.
- Catalogue
- M26
- Type
- Open cluster
- Constellation
- Scutum
- Distance
- 5,000 light-years
- Apparent magnitude
- 8.0
- Surface brightness
- 22.5 mag/□″
- Apparent size
- 15′
- Right ascension
- 18h 45m
- Declination
- −9.40°
- Found by
- Charles Messier, 1764
Magnitude 8.0 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 10×50 binoculars from Bortle 9.
| Sky | Eye | 10×50 | 80mm | 130mm | 200mm |
|---|---|---|---|---|---|
| Bortle 1 21.9 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 2 21.7 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 3 21.4 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 4 20.9 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 5 20.3 mag/□″ | No | 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
Modest by any measure, with perhaps twenty-five stars at 150mm and a noticeably empty patch near the middle. The comparison with M11 four degrees away is unkind and unavoidable. Worth seeing once so that the comparison means something.
When, and from where
Highest in the middle of the night in July. Close enough to the celestial equator to rise from almost anywhere on Earth, and to pass overhead for anyone near 9°S.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 21° | |
| 51°N London, Calgary | 30° | |
| 40°N New York, Madrid | 41° | |
| 30°N Cairo, Houston | 51° | |
| 0°N the equator | 81° | |
| 33°S Sydney, Cape Town | 66° |
Nearby in the sky
The whole catalogue →One more of the catalogue sits within five degrees, close enough to take in on the same night without moving far. Everything below is measured from M26 itself, not from the middle of Scutum.
- M11 Wild Duck Cluster 3.5° apart Scutum · magnitude 6.3 · binoculars from Bortle 9 or darker
- M16 Eagle Nebula 7.8° apart Serpens · magnitude 6.0 · binoculars from Bortle 2 or darker
- M17 Omega Nebula 9.0° apart Sagittarius · magnitude 6.0 · needs more than binoculars
- M18 Open cluster 9.9° apart Sagittarius · magnitude 7.5 · binoculars from Bortle 9 or darker
One of 110. Positions J2000; the sky is the final authority.