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Pacman Nebula (NGC 281)
emission nebula in Cassiopeia
The Pacman Nebula is an emission nebula in Cassiopeia, shaped a bit like the arcade character. Dark Bok globules of dust and a young cluster of hot stars sit inside it.
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// Key facts
- Catalog
- NGC 281
- Type
- emission nebula
- Constellation
- Cassiopeia
- Size
- 35′ across
- Brightness
- Magnitude 7.4
- Distance
- about 9,500 light-years
- Peak month (any location)
- Oct
- Typical prime months
- Jul to Dec
- Difficulty
- Intermediate
- Filter
- Narrowband: Ha / OIII / SII, or a dual-band / UHC filter
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How to image Pacman Nebula
- Ha, OIII and SII narrowband give strong results.
- At 35 arcminutes, 500 to 800 mm frames it nicely.
- High in the sky from northern sites in autumn and winter.
Framing: what focal length?
The focal length at which NGC 281 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 780 mm |
| APS-C (23.5 mm) | about 1380 mm |
| Full frame (36 mm) | about 2120 mm |
How high does it climb from your latitude?
The highest point NGC 281 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) | 88° | High in the sky |
| 45°N (Minneapolis, Milan) | 78° | High in the sky |
| 35°N (Los Angeles, Tokyo) | 68° | High in the sky |
| 25°N (Miami, Cairo) | 58° | Workable |
| 35°S (Sydney, Santiago) | below horizon | Never rises |
Also worth imaging
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