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M12
globular cluster in Ophiuchus
M12 is a globular cluster in Ophiuchus with a looser, less concentrated core than most, so the individual stars spread out and are easier to resolve. It sits about three degrees from M10, and the two work well together.
Save your telescope or lens on the planner to lay your camera frame over this diagram.
// Key facts
- Catalog
- M12
- Type
- globular cluster
- Constellation
- Ophiuchus
- Size
- 16′ across
- Brightness
- Magnitude 6.7
- Distance
- about 15,700 light-years
- Peak month (any location)
- Jun
- Typical prime months
- Mar to Aug
- Difficulty
- Beginner
- Filter
- No filter (broadband)
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How to image M12
- Combine it with M10 in one wide frame, or shoot it alone at 800 to 1,200 mm.
- Because the core is looser, it clips less than most globulars, which makes it forgiving for exposure choices.
- Ophiuchus is best around summer evenings and the cluster is moderately low from northern sites.
Framing: what focal length?
M12 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 20% |
| 2,000 mm | about 40% |
| 3,000 mm | about 59% |
How high does it climb from your latitude?
The highest point M12 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) | 33° | Workable |
| 45°N (Minneapolis, Milan) | 43° | Workable |
| 35°N (Los Angeles, Tokyo) | 53° | Workable |
| 25°N (Miami, Cairo) | 63° | High in the sky |
| 35°S (Sydney, Santiago) | 57° | Workable |
Also worth imaging
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