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Horsehead Nebula (IC 434)
emission nebula in Orion
The Horsehead Nebula is a dark dust cloud shaped like a horse's head, silhouetted against a faint red glow of hydrogen. It is small and dim, and right next to the very bright star Alnitak and the Flame Nebula (NGC 2024), which both throw glare across the field. It is a favorite goal for narrowband imagers.
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// Key facts
- Catalog
- IC 434
- Type
- emission nebula
- Constellation
- Orion
- Size
- 1.0° across
- Brightness
- Magnitude 6.8
- Distance
- about 1,400 light-years
- Peak month (any location)
- Dec
- Typical prime months
- Oct to Feb
- Difficulty
- Advanced
- Filter
- Ha narrowband (the Horsehead is dark dust against Ha glow)
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How to image Horsehead Nebula
- A hydrogen-alpha filter is the key: the Horsehead only shows against Ha glow.
- Use 800 mm or more to make it a real feature, or a wider frame to include the Flame.
- Bright Alnitak causes reflections and halos, so careful flats and a clean optical path help.
Framing: what focal length?
The focal length at which IC 434 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 450 mm |
| APS-C (23.5 mm) | about 810 mm |
| Full frame (36 mm) | about 1240 mm |
How high does it climb from your latitude?
The highest point IC 434 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) | 33° | Workable |
| 45°N (Minneapolis, Milan) | 43° | Workable |
| 35°N (Los Angeles, Tokyo) | 53° | Workable |
| 25°N (Miami, Cairo) | 63° | High in the sky |
| 35°S (Sydney, Santiago) | 57° | Workable |
Also worth imaging
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