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M71
globular cluster in Sagitta
M71 is a small, loose globular cluster in Sagitta, so open in structure that for a long time it was debated whether it was a globular or a dense open cluster. It sits in a rich Milky Way field and is easy to resolve into stars.
Save your telescope or lens on the planner to lay your camera frame over this diagram.
// Key facts
- Catalog
- M71
- Type
- globular cluster
- Constellation
- Sagitta
- Size
- 7′ across
- Brightness
- Magnitude 8.2
- Distance
- about 13,000 light-years
- Peak month (any location)
- Jul
- Typical prime months
- May to Oct
- Difficulty
- Intermediate
- Filter
- No filter (broadband)
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How to image M71
- Only 7 arcminutes across, so 1,000 mm or more frames it as a target.
- M27, the Dumbbell Nebula, is a few degrees away and a wide frame can show both.
- It is well placed from northern sites in summer evenings.
Framing: what focal length?
M71 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 9% |
| 2,000 mm | about 17% |
| 3,000 mm | about 26% |
How high does it climb from your latitude?
The highest point M71 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) | 54° | Workable |
| 45°N (Minneapolis, Milan) | 64° | High in the sky |
| 35°N (Los Angeles, Tokyo) | 74° | High in the sky |
| 25°N (Miami, Cairo) | 84° | High in the sky |
| 35°S (Sydney, Santiago) | 36° | Workable |
Also worth imaging
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