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47 Tucanae (NGC 104)
globular cluster in Tucana
47 Tucanae is the second-brightest globular cluster in the sky after Omega Centauri, with a dense, bright core and millions of stars. It sits close to the Small Magellanic Cloud. It is a southern target.
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// Key facts
- Catalog
- NGC 104
- Also known as
- C 106, Caldwell 106, 47 Tuc
- Type
- globular cluster
- Constellation
- Tucana
- Size
- 50′ across
- Brightness
- Magnitude 4
- Distance
- about 13,000 light-years
- Peak month (any location)
- Sep
- Typical prime months
- Jul to Dec
- Difficulty
- Beginner
- Filter
- No filter (broadband)
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How to image 47 Tucanae
- Use 500 to 1,000 mm; it is about 50 arcminutes across including its outer stars.
- No filter is needed. Short exposures keep the core from clipping.
- It never rises north of about 18 degrees north, so it is only visible from the tropics southward.
Framing: what focal length?
The focal length at which NGC 104 spans about 60% of the long side of the sensor, leaving room around it. Treat it as a starting point; the right framing is a matter of taste.
| Sensor | Focal length |
|---|---|
| 1-inch sensor (13.2 mm) | about 540 mm |
| APS-C (23.5 mm) | about 970 mm |
| Full frame (36 mm) | about 1490 mm |
How high does it climb from your latitude?
The highest point NGC 104 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) | below horizon | Never rises |
| 35°S (Sydney, Santiago) | 53° | Workable |
Also worth imaging
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