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Jellyfish Nebula (IC 443)
supernova remnant in Gemini
The Jellyfish Nebula is the remains of a supernova in Gemini, a curved shell of delicate filaments that looks like a jellyfish. It is a faint supernova remnant, close to the bright star Eta Geminorum. It is a rewarding narrowband target.
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// Key facts
- Catalog
- IC 443
- Type
- supernova remnant
- Constellation
- Gemini
- Size
- 50′ across
- Brightness
- Magnitude 12
- Distance
- about 5,000 light-years
- Peak month (any location)
- Dec
- Typical prime months
- Oct to Mar
- Difficulty
- Advanced
- Filter
- OIII + Ha narrowband
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How to image Jellyfish Nebula
- Use 600 to 1,000 mm; it is about 50 arcminutes across.
- Narrowband is needed: Ha and OIII bring out the filaments.
- Winter evenings are the best season.
Framing: what focal length?
The focal length at which IC 443 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 540 mm |
| APS-C (23.5 mm) | about 970 mm |
| Full frame (36 mm) | about 1490 mm |
How high does it climb from your latitude?
The highest point IC 443 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) | 58° | Workable |
| 45°N (Minneapolis, Milan) | 68° | High in the sky |
| 35°N (Los Angeles, Tokyo) | 78° | High in the sky |
| 25°N (Miami, Cairo) | 88° | High in the sky |
| 35°S (Sydney, Santiago) | 32° | Workable |
Also worth imaging
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