Caldwell 94 — Open Cluster in Crux
NGC 4755
About Jewel Box
Description
The Jewel Box (NGC 4755) is a brilliant open cluster in Crux, about 6,440 light-years away. Named by John Herschel, who compared it to a piece of fancy jewelry with its striking array of blue, white, and red supergiants clustered within 10 arcminutes. It is visible to the naked eye at magnitude 4.2.
Observing Tips
One of the most beautiful open clusters in the sky. A telescope at 50-100x reveals the famous color contrasts — the red supergiant Kappa Crucis stands out against brilliant blue-white companions. Binoculars show a bright, condensed group near Beta Crucis. Best from southern latitudes in autumn and winter.
History
Discovered by Nicolas Louis de Lacaille in 1751. John Herschel named it the Jewel Box during his southern sky survey, describing it as "a casket of variously coloured precious stones."
Fun Facts
The Jewel Box is only about 14 million years old. The bright red supergiant Kappa Crucis (DU Crucis) has already evolved off the main sequence despite the cluster's youth, indicating it is one of the most massive stars in the cluster at about 20 solar masses.
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: ESO/Y. Beletsky. License: CC BY 4.0. (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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