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Bubble Nebula (NGC 7635)
emission nebula in Cassiopeia
The Bubble Nebula in Cassiopeia is a bubble of gas blown by the strong wind of a hot young star. It is faint and small, but sits next to a bright open cluster, M52, which makes a good wide-field companion.
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// Key facts
- Catalog
- NGC 7635
- Type
- emission nebula
- Constellation
- Cassiopeia
- Size
- 15′ across
- Brightness
- Magnitude 10
- Distance
- about 7,100 light-years
- Peak month (any location)
- Sep
- Typical prime months
- Jun to Nov
- Difficulty
- Intermediate
- Filter
- Narrowband: Ha / OIII / SII, or a dual-band / UHC filter
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How to image Bubble Nebula
- Ha and OIII bring out the bubble, which can look faint in broadband.
- At 15 arcminutes, use 800 to 1,200 mm.
- It is high in the sky on autumn evenings from northern sites.
Framing: what focal length?
NGC 7635 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 19% |
| 2,000 mm | about 37% |
| 3,000 mm | about 56% |
How high does it climb from your latitude?
The highest point NGC 7635 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) | 84° | High in the sky |
| 45°N (Minneapolis, Milan) | 74° | High in the sky |
| 35°N (Los Angeles, Tokyo) | 64° | High in the sky |
| 25°N (Miami, Cairo) | 54° | Workable |
| 35°S (Sydney, Santiago) | below horizon | Never rises |
Also worth imaging
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