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Hubble's Variable Nebula (NGC 2261)
reflection nebula in Monoceros
Hubble's Variable Nebula is a small, fan-shaped reflection nebula in Monoceros lit by the young star R Monocerotis. It changes in brightness and shape over weeks and months, which makes it a fun target to revisit. It sits close to the Cone Nebula and Rosette.
Save your telescope or lens on the planner to lay your camera frame over this diagram.
// Key facts
- Catalog
- NGC 2261
- Also known as
- C 46, Caldwell 46
- Type
- reflection nebula
- Constellation
- Monoceros
- Size
- 2′ across
- Brightness
- Magnitude 9
- Distance
- about 2,500 light-years
- Peak month (any location)
- Dec
- Typical prime months
- Oct to Mar
- Difficulty
- Intermediate
- Filter
- No filter (broadband); a UV/IR-cut or L filter is enough
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How to image Hubble's Variable Nebula
- It is only about 2 arcminutes across, so use 1,000 to 2,000 mm.
- No filter is needed; use a clean luminance or UV/IR cut.
- Compare images across several months to catch it changing.
Framing: what focal length?
NGC 2261 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 2% |
| 2,000 mm | about 5% |
| 3,000 mm | about 7% |
How high does it climb from your latitude?
The highest point NGC 2261 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) | 44° | Workable |
| 45°N (Minneapolis, Milan) | 54° | Workable |
| 35°N (Los Angeles, Tokyo) | 64° | High in the sky |
| 25°N (Miami, Cairo) | 74° | High in the sky |
| 35°S (Sydney, Santiago) | 46° | Workable |
Also worth imaging
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