Ptolemy´s Cluster
open cluster · Scorpius · 3.3ᵐ
Ptolemy’s Cluster has been known since antiquity — Claudius Ptolemy described it around AD 130 as a nebula following the sting of Scorpius.
Notable facts
Covers about 2.6 times more sky than the Moon.
In brief
Which constellation is Ptolemy´s Cluster in?
Ptolemy´s Cluster lies in Scorpius.
Is Ptolemy´s Cluster visible to the naked eye?
3.3ᵐ — visible to the naked eye (under dark skies).
When is the best time to observe Ptolemy´s Cluster?
Best observed in June.
Data
- RA / Dec (J2000)
- 17h 54m · −34° 49′
- Type
- open cluster
- Constellation
- Scorpius
- How to observe
- 3.3ᵐ — visible to the naked eye (under dark skies)
- Angular size
- 80′
- Designation
- M7 · NGC 6475 · Ptolemy´s Cluster
Observing tip
Best in binoculars or a telescope at low power, so the whole cluster fits in the field of view.
Altitude above the horizon by latitude
| Latitude | Maximum altitude | Rise azimuth |
|---|---|---|
| +60° | never rises | — |
| +55° | 0° | 175° |
| +45° | 10° | 144° |
| +30° | 25° | 131° |
| 0° | 55° | 125° |
| −35° | 90° | 134° |
Geometric altitude at upper culmination, atmospheric refraction not included. Positive latitudes are in the northern hemisphere.
Culmination time by month
| Month | Culmination |
|---|---|
| January | 10:08 |
| February | 08:01 |
| March | 06:16 |
| April | 04:22 |
| May | 02:28 |
| June | 00:22 |
| July | 22:18 |
| August | 20:17 |
| September | 18:24 |
| October | 16:35 |
| November | 14:35 |
| December | 12:26 |
Upper culmination in local solar time — no time-zone or daylight-saving correction applied.