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Starfish Cluster (M38)
open cluster in Auriga
M38, the Starfish Cluster, is a large open cluster in Auriga with a pattern of stars that look like a starfish or a cross. A smaller, fainter cluster, NGC 1907, sits half a degree away.
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// Key facts
- Catalog
- M38
- Type
- open cluster
- Constellation
- Auriga
- Size
- 21′ across
- Brightness
- Magnitude 6.4
- Distance
- about 4,200 light-years
- Peak month (any location)
- Dec
- Typical prime months
- Sep to Feb
- Difficulty
- Beginner
- Filter
- No filter (broadband)
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How to image Starfish Cluster
- At 21 arcminutes, 500 to 800 mm frames it, and NGC 1907 fits in the same field.
- Combine it with M36 and M37 for a wide mosaic of Auriga.
- It is high in winter evenings from northern sites.
Framing: what focal length?
The focal length at which M38 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 1300 mm |
| APS-C (23.5 mm) | about 2310 mm |
| Full frame (36 mm) | about 3540 mm |
How high does it climb from your latitude?
The highest point M38 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) | 71° | High in the sky |
| 45°N (Minneapolis, Milan) | 81° | High in the sky |
| 35°N (Los Angeles, Tokyo) | 89° | High in the sky |
| 25°N (Miami, Cairo) | 79° | High in the sky |
| 35°S (Sydney, Santiago) | 19° | Stays low |
Also worth imaging
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