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Gamma Cygni Nebula (IC 1318)
emission nebula in Cygnus
The Gamma Cygni Nebula, or Butterfly Nebula, is a wide area of glowing gas around the bright star Sadr, in the center of the Northern Cross in Cygnus. It spans several degrees and is full of dark dust lanes. It is a perfect widefield target for a lens or short refractor.
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// Key facts
- Catalog
- IC 1318
- Type
- emission nebula
- Constellation
- Cygnus
- Size
- 3.0° across
- Brightness
- Magnitude 8
- Distance
- about 5,000 light-years
- Peak month (any location)
- Jul
- Typical prime months
- May to Oct
- Difficulty
- Intermediate
- Filter
- Narrowband: Ha / OIII / SII, or a dual-band / UHC filter
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How to image Gamma Cygni Nebula
- Use 135 to 300 mm; the whole region is about 3 degrees.
- Hydrogen-alpha works well; broadband adds the star field.
- Sadr is very bright and can cause halos, so keep an eye on reflections.
Framing: what focal length?
The focal length at which IC 1318 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 150 mm |
| APS-C (23.5 mm) | about 270 mm |
| Full frame (36 mm) | about 410 mm |
How high does it climb from your latitude?
The highest point IC 1318 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) | 75° | High in the sky |
| 45°N (Minneapolis, Milan) | 85° | High in the sky |
| 35°N (Los Angeles, Tokyo) | 85° | High in the sky |
| 25°N (Miami, Cairo) | 75° | High in the sky |
| 35°S (Sydney, Santiago) | 15° | Stays low |
Also worth imaging
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