NGC 663, mag. +7.1, is a young open cluster that's one of a number of bright clusters that can be seen with binoculars in the constellation of Cassiopeia. It contains at least 80 stars visible in amateur telescopes spread over a diameter of 16 arc minutes. A 100mm (4-inch) scope reveals a bright rich grouping immersed in a hazy glow with many stars resolvable. NGC 663 is striking in larger scopes appearing reasonably concentrated towards the centre with dozens of stars spread across the cluster face. Double star Struve 152 is a cluster member.
NGC 663 is located 3 degrees northeast of Ruchbah (δ Cas - mag. +2.7) and 3 degrees southwest of epsilon Cas (ε Cas - mag. +3.4). Positioned just north of the cluster is NGC 654 (mag. +6.5) with NGC 659 (mag. +7.9) to the south. Also located nearby next to Ruchbah is M103 (mag. +7.4). All of these open clusters are visible in binoculars.
From most northern temperate latitudes NGC 663 is circumpolar and therefore visible all year round; it appears highest in the sky during October, November and December. From Southern Hemisphere latitudes the cluster appears at best low above the northern horizon and from some more southerly locations it never even rises at all.
NGC 663 is located 7,000 light-years distant. It's estimated to be 20 Million years old and is number 10 in the Caldwell catalogue. The cluster was discovered by William Herschel on November 3, 1787. It's believed to form part of the stellar association Cassiopeia OB8, which also contains M103, NGC 654, NGC 659 and some supergiant stars scattered between them. NGC 663 is interesting to professional astronomers as it also contains a high number of Be stars and some blue stragglers.
NGC 663 Data Table
|Object Type||Open Cluster|
|RA (J2000)||01h 46m 16s|
|DEC (J2000)||61d 13m 06s|
|Apparent Size (arc mins)||16 x 16|
|Age (years)||20 Million|
|Number of Stars||>80|
|Other Name||Collinder 20|