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King Cobra Cluster (M67)
open cluster in Cancer
M67 is one of the oldest known open clusters, around four billion years old, which is why it has survived when most open clusters have drifted apart. It lies well above the plane of the Milky Way, near the Beehive, and holds several hundred stars.
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// Key facts
- Catalog
- M67
- Type
- open cluster
- Constellation
- Cancer
- Size
- 30′ across
- Brightness
- Magnitude 6.1
- Distance
- about 2,700 light-years
- Peak month (any location)
- Feb
- Typical prime months
- Nov to Apr
- Difficulty
- Beginner
- Filter
- No filter (broadband)
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How to image King Cobra Cluster
- At 30 arcminutes, 500 to 800 mm frames it nicely.
- It is a good target for a bright moon when galaxies are impractical.
- High in the sky on spring evenings from northern sites.
Framing: what focal length?
The focal length at which M67 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 910 mm |
| APS-C (23.5 mm) | about 1620 mm |
| Full frame (36 mm) | about 2480 mm |
How high does it climb from your latitude?
The highest point M67 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) | 47° | Workable |
| 45°N (Minneapolis, Milan) | 57° | Workable |
| 35°N (Los Angeles, Tokyo) | 67° | High in the sky |
| 25°N (Miami, Cairo) | 77° | High in the sky |
| 35°S (Sydney, Santiago) | 43° | Workable |
Also worth imaging
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