Your deep sky companionYour deep sky imaging companion
Jewel Box Cluster (NGC 4755)
open cluster in Crux
The Jewel Box is a small, bright open cluster in Crux (the Southern Cross) with stars in several colors, including a striking red supergiant. It is one of the most colorful clusters in the sky. It is a southern target.
Save your telescope or lens on the planner to lay your camera frame over this diagram.
// Key facts
- Catalog
- NGC 4755
- Also known as
- C 94, Caldwell 94
- Type
- open cluster
- Constellation
- Crux
- Size
- 10′ across
- Brightness
- Magnitude 4.2
- Distance
- about 6,400 light-years
- Peak month (any location)
- Apr
- Typical prime months
- Jan to Jun
- Difficulty
- Beginner
- Filter
- No filter (broadband)
Pick a saved location or share your device location. Your coordinates are used only to calculate tonight and are not stored. To save locations, use the planner.
How to image Jewel Box Cluster
- Use 800 to 1,500 mm; it is about 10 arcminutes across.
- No filter is needed. Short exposures preserve star colors.
- It never rises north of about 30 degrees north, so it is for southern latitudes.
Framing: what focal length?
NGC 4755 is small, so a "60% of the frame" focal length would be impractical. Here is how much of an APS-C frame it covers at common long focal lengths; expect to crop.
| Focal length | Share of the frame width |
|---|---|
| 1,000 mm | about 12% |
| 2,000 mm | about 25% |
| 3,000 mm | about 37% |
How high does it climb from your latitude?
The highest point NGC 4755 reaches in the sky. Above about 60° is excellent, 30° to 60° is workable, and under 30° you are looking through a lot of air.
| Latitude | Highest point | Rating |
|---|---|---|
| 55°N (Scotland, Alaska) | below horizon | Never rises |
| 45°N (Minneapolis, Milan) | below horizon | Never rises |
| 35°N (Los Angeles, Tokyo) | below horizon | Never rises |
| 25°N (Miami, Cairo) | 5° | Stays low |
| 35°S (Sydney, Santiago) | 65° | High in the sky |
Also worth imaging
Want a GO / NO-GO verdict for tonight, with clouds, moon, seeing and a full dark-window timeline?
Open the planner