Ptolemy Cluster (M7)
A large, bright open cluster in Scorpius, easily visible to the naked eye and known since antiquity.
Open cluster in Scorpius. Magnitude 3.3.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 48° above the southern horizon at its highest; from Lethem (3.4° N), to 52° above the southern horizon. It is highest at midnight on the night of 18 Jun, in the middle of its season. The page works out tonight's rise, highest point and set for both towns in Guyana time (UTC-4), and where the Moon is.
What you'll see
- Your eyes: Visible to the eye even from Georgetown, as a loose group of stars.
- 10x50 binoculars: Resolves into dozens of stars.
- A small telescope (80 to 100 mm): Too big for most telescope fields; binoculars show it better.
- A camera: Spans about 40% of an APS-C frame at 400 mm (field 3.4° × 2.2°); needs a tracking mount.
How big, how bright, how far
- Size on the sky: 80′, 2.6 Moons across (the Moon is about 31′ wide).
- Brightness: magnitude 3.3. Brighter than the faintest stars Georgetown shows (4.3), and Lethem's (6.0).
- Distance: 980 light-years. The light reaching your eye left it about 980 years ago, around the year 1050.
What it is made of
- Type
- Open Cluster
- Distance
- Approx. 980 Lightyears
- True size
- Approx. 25 Lightyears diameter
- Young Hot Stars: B-type, recently formed
More deep-sky objects: Butterfly Cluster (M6) · NGC 6231 (Northern Jewel Box) · Globular Cluster M22 · M25 (Open Cluster IC 4725) · Globular Cluster M4 · Eagle Nebula (M16)