Caldwell 56 — Planetary Nebula in Cetus
NGC 246
About C56
Description
NGC 246 is a planetary nebula in Cetus, about 1,600 light-years away. Known as the Skull Nebula, it has a large, ghostly shell about 4 arcminutes across with a distinctly mottled, uneven surface that gives it a skull-like appearance.
Observing Tips
A large but faint planetary nebula. An 8-inch telescope with an OIII filter shows the round, uneven glow. The 12th-magnitude central star is a hot white dwarf in a binary system. Best in autumn evenings.
History
Discovered by William Herschel on November 27, 1785. The central star is actually a close binary system, which may influence the nebula's complex internal structure.
Fun Facts
NGC 246 is one of the nearest planetary nebulae to Earth and one of the largest in angular size. Its central star is one of the hottest white dwarfs known, at about 150,000 K.
Observe
1Properties
Position & Identifiers
2How easy to spot?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | V. hard+ | V. hard | Imp. |
| 150 mm Newton 150mm Newt. | Hard+ | Hard | V. hard+ |
| Celestron C8 (203 mm SCT) C8 203mm | Hard+ | Hard+ | Hard |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
With O-III filter
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Hard+ | Hard | V. hard+ |
| 150 mm Newton 150mm Newt. | Medium | Medium | Hard+ |
| Celestron C8 (203 mm SCT) C8 203mm | Medium+ | Medium | Medium |
3Visibility
Set a location in User Settings to see visibility data.
4
Filter Response Guide
5
Eyepiece View
6
Best Magnification
Explore
7
Central Star
8
Surface Brightness
Discover
9
Light Travel Time Machine
10
Relativistic Travel
Community Photos (1)
Credit: Unknown. License: Public domain. (Wikimedia Commons)
Skybred Mar 2, 2026
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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