Caldwell 2 — Planetary Nebula in Cepheus
NGC 40
About Bow Tie Nebula
Description
The Bow Tie Nebula (NGC 40) is a planetary nebula in Cepheus, about 3,500 light-years away. Its central star is one of the hottest known, at about 50,000 K, and drives a fast stellar wind that shapes the nebula into its distinctive barrel or bow-tie shape spanning roughly 1 arcminute.
Observing Tips
Requires at least a 4-inch telescope to spot as a fuzzy star. A 6- to 8-inch scope reveals its slightly elongated shape. An OIII filter helps enhance contrast. Best observed in autumn and winter evenings from northern latitudes.
History
Discovered by William Herschel on November 25, 1788. The nebula is notable for its hot central star, which is still in an active mass-loss phase. The name comes from its shape in deep images.
Fun Facts
The central star of NGC 40 is a Wolf-Rayet type star that is rapidly shedding its outer layers. In about 30,000 years, the nebula will have dissipated entirely, and the star will become a white dwarf.
Observe
1Properties
Position & Identifiers
2How easy to spot?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Imp. | Imp. | Imp. |
| 150 mm Newton 150mm Newt. | V. hard+ | V. hard | V. hard |
| Celestron C8 (203 mm SCT) C8 203mm | Hard | V. hard+ | V. 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. | V. hard+ | V. hard | V. hard |
| 150 mm Newton 150mm Newt. | Hard+ | Hard | Hard |
| Celestron C8 (203 mm SCT) C8 203mm | Hard+ | Hard+ | Hard |
3Visibility
Set a location in User Settings to see visibility data.
4
Filter Response Guide
5
Eyepiece View
Bow Tie Nebula · 0.8′ · N up, E left
6
Best Magnification
Explore
7
Central Star
8
Surface Brightness
Discover
9
Light Travel Time Machine
10
Relativistic Travel
Community Photos (1)
Credit: Meli thev. License: CC BY-SA 4.0. (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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