Deep Sky Object of the Month

Commonly known as the Crescent Nebula, NGC 6888 in Cygnus is a beautiful sight in medium to large telescopes under dark skies. (Left) POSS/DSS photo, (right) drawing made in 1993 by Robert Kerwin using an eight-inch reflector.

Lying in one of the most fascinating areas of the Milky Way, NGC 6888 is a beautiful sight in 8-inch and larger telescopes. Though not quite as famous as its neighbors to the east and north (Veil Nebula and North America Nebula), the Crescent Nebula is actually rather bright and shows much detail to the patient observer under dark skies.

Although it's called the Crescent Nebula, visually it's not hard to see the complete bubble, which is about 20' across and extended northeast-southwest. Brighter clumps of nebulosity to the north and east form the arc that gives this object its name. Overall, the crescent is about 120° long. If you have good skies and at least a 12-inch scope, you may be able to detect some blotchiness in the fainter parts of the nebula. Try using a nebula filter (such as a UHC) to boost the contrast.

The Crescent Nebula is technically known as a Wolf-Rayet nebula. The star that formed the bubble went through a phase in its evolution where it lost considerable mass through a dense stellar wind. As the star contracted and became hotter, the stellar wind became more rarefied, but faster. This fast stellar wind swept up the more dense material blown out earlier, forming a bubble of glowing gas.

How to get there:

NGC 6888 is about three degrees southwest of Gamma Cygni, or one-third of the distance from Gamma to Eta Cygni.

Finder chart for NGC 6888