Caldwell 71 — Open Cluster in Puppis
NGC 2477
About C71
Description
NGC 2477 is one of the richest open clusters in the sky, located in Puppis about 3,600 light-years away. It contains roughly 300 stars within a diameter of 27 arcminutes and has sometimes been mistaken for a globular cluster due to its dense concentration.
Observing Tips
A spectacular cluster in any telescope. Binoculars show a rich, hazy patch. A 4-inch telescope resolves dozens of stars, and an 8-inch scope at 80-120x is breathtaking with hundreds of stars filling the field. Best in winter evenings.
History
Discovered by Nicolas Louis de Lacaille in 1751 from South Africa during his southern sky survey. It is considered one of the finest open clusters in the southern sky.
Fun Facts
NGC 2477 is about 700 million years old and so rich that its total mass and density approach those of a sparse globular cluster. It is one of the most massive open clusters in the Milky Way.
Observe
1Properties
Position & Identifiers
2How easy to spot?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Easy | Easy | Easy |
| 150 mm Newton 150mm Newt. | Easy | Easy | Easy |
| Celestron C8 (203 mm SCT) C8 203mm | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
3Visibility
Set a location in User Settings to see visibility data.
4
Eyepiece View
5
Best Magnification
6Where this cluster sits in time
Open clusters span more than four orders of magnitude in age — from newborn OB associations to ancient, metal-rich survivors.
7
Colour-Magnitude Diagram
A cluster's colour-magnitude diagram reveals its age: the bluer the turn-off point where the main sequence bends into red giants, the younger the cluster.
Each point is a Gaia-DR3 member. Colour encodes spectral type; size reflects membership probability.
Explore
8
Classification Decoder
Discover
9
Light Travel Time Machine
10
Relativistic Travel
Community Photos (1)
Credit: Guillermo Abramson. License: CC BY 3.0. (Wikimedia Commons)
Skybred Mar 2, 2026
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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