Caldwell 27 — Emission Nebula in Cygnus
NGC 6888
About Crescent Nebula
Description
The Crescent Nebula (NGC 6888) is an emission nebula in Cygnus, about 5,000 light-years away. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 colliding with slower material the star ejected when it was a red supergiant.
Observing Tips
A challenging visual target. An OIII filter is almost essential, revealing the crescent-shaped arc in an 8-inch or larger telescope. Located near the center of Cygnus in the rich Milky Way, which provides a spectacular star field. Best in summer.
History
Discovered by William Herschel on September 15, 1792. The nebula is a textbook example of a wind-blown bubble created by a massive star's violent final evolutionary stages before it eventually explodes as a supernova.
Fun Facts
The Wolf-Rayet star WR 136 at the center is losing mass at a staggering rate and will likely explode as a supernova within a few hundred thousand years. The nebula is expanding at about 75 km/s.
Observe
1Properties
Position & Identifiers
2How easy to spot?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Medium | Hard | V. hard+ |
| 150 mm Newton 150mm Newt. | Medium+ | Medium | Medium |
| Celestron C8 (203 mm SCT) C8 203mm | Medium+ | Medium+ | Medium |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
With O-III filter
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Medium+ | Medium | Hard+ |
| 150 mm Newton 150mm Newt. | Easy | Easy | Medium+ |
| Celestron C8 (203 mm SCT) C8 203mm | Easy | Easy | Easy |
3Visibility
Set a location in User Settings to see visibility data.
4
Filter Response Guide
5
Eyepiece View
Crescent Nebula · 20.0′×10.0′ · N up, E left
Explore
6
Surface Brightness
Discover
7
Light Travel Time Machine
8
Relativistic Travel
Community Photos (1)
Credit: Chuck Ayoub. License: CC0. (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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