Open cluster · Ophiuchus
NGC 6633 Tweedledum Cluster
mag 4.612′ across
About
NGC 6633, the Tweedledum Cluster, is an open cluster of magnitude 4.6 in Ophiuchus, about 12′ across.
How to find it
- NGC 6633 is in the constellation Ophiuchus.
- Best evenings: around mid-August it is highest at about 9 pm (10 pm in summer time); a month earlier, two hours later.
- Where on Earth: it is seen well, at least 10° up, from north of 73° S.
When it rises and sets tonight, how high it climbs and how much the Moon gets in the way are worked out in your browser for your place.
What you will see
- EyesA faint smudge at the limit of vision, only from a dark site.
- Binoculars (10×50)A small knot of stars, partly resolved.
- Telescope (6–8 inch)Dozens of stars, many sharp and some coloured.
For a dark country sky with no Moon. From a city, faint galaxies and nebulae can disappear completely.
Facts
| Designations | NGC 6633 |
|---|---|
| Type | Open cluster |
| Magnitude | 4.6The smaller the number, the brighter. |
| Apparent size | 12′the full Moon is 31′ across |
| Constellation | Ophiuchus |
| Right ascension (J2000) | 18h 27m 15.2s |
| Declination (J2000) | +06° 30′ 30″ |
Sources and credits
Catalog data: OpenNGC by Mattia Verga, CC BY-SA 4.0, and d3-celestial by Olaf Frohn, BSD 3-Clause. All data sources →