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C10

NGC 663

Open Cluster Excellent (73/100)
C10 OpenCluster Cassiopeia Visible Level 1 Naked eye / Binoculars - Wide field preferred
Credit: Hewholooks. License: CC BY-SA 3.0. (Wikimedia Commons)
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Properties

Magnitude 7.1
Angular Size 6.0′
Distance 6800 ly
Open Cluster [Distance: 6800 ly]

Position & Identifiers

RA 01h 42m 36.0s
Dec +61° 15' 00.0"
Constellation Cassiopeia
Catalog C10

Visibility

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About C10

Description

NGC 663 is a bright, rich open cluster in Cassiopeia, about 6,850 light-years away. It contains over 400 stars spread across 16 arcminutes, with many hot blue B-type stars and several red supergiants.

Observing Tips

An easy and rewarding target, visible in binoculars as a hazy patch and stunning in small telescopes. A 4-inch scope at 50-80x reveals dozens of stars. Circumpolar from northern latitudes, best placed in autumn.

History

Discovered in 1654 by Giovanni Battista Hodierna. Independently found by William Herschel in 1787. One of the finest open clusters in Cassiopeia.

Fun Facts

NGC 663 is only about 20-25 million years old. It contains an unusual number of Be stars — rapidly rotating hot stars with circumstellar disks — making it ideal for studying this phenomenon.

Community Photos (1)

Credit: Hewholooks. License: CC BY-SA 3.0. (Wikimedia Commons)

Credit: Hewholooks. License: CC BY-SA 3.0. (Wikimedia Commons)

Skybred Mar 2, 2026