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M9
globular cluster in Ophiuchus
M9 is a small, dense globular cluster in Ophiuchus, close to the center of the Milky Way. It sits in a rich star field, and the dust between it and us makes it look a little dimmer and redder than it really is.
Save your telescope or lens on the planner to lay your camera frame over this diagram.
// Key facts
- Catalog
- M9
- Type
- globular cluster
- Constellation
- Ophiuchus
- Size
- 12′ across
- Brightness
- Magnitude 7.9
- Distance
- about 25,800 light-years
- Peak month (any location)
- Jun
- Typical prime months
- Mar to Aug
- Difficulty
- Intermediate
- Filter
- No filter (broadband)
Pick a saved location or share your device location. Your coordinates are used only to calculate tonight and are not stored. To save locations, use the planner.
How to image M9
- It is only 12 arcminutes across, so 1,000 mm or more frames it as a real target rather than a star in a field.
- Dec -18 puts it low from the northern United States and Canada, so aim for the hours when it crosses the meridian.
- A dense star field makes accurate guiding and round stars important.
Framing: what focal length?
M9 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 15% |
| 2,000 mm | about 30% |
| 3,000 mm | about 45% |
How high does it climb from your latitude?
The highest point M9 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) | 16° | Stays low |
| 45°N (Minneapolis, Milan) | 26° | Stays low |
| 35°N (Los Angeles, Tokyo) | 36° | Workable |
| 25°N (Miami, Cairo) | 46° | Workable |
| 35°S (Sydney, Santiago) | 74° | High in the sky |
Also worth imaging
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