NGC 663, cataloged as Caldwell 10 and Melotte 11, is a rich open star cluster in Cassiopeia that shines at magnitude 7.1, bright enough to make an inviting target for wide-field astrophotography. Spanning about 18′ across the sky, it fits comfortably within the field of view of short to medium focal-length telescopes and telephoto lenses, leaving room to frame the surrounding star fields. Its dense scattering of blue-white stars renders beautifully against the crowded Milky Way backdrop of this region, rewarding exposures that preserve subtle stellar color. Because the cluster sits amid a bright and busy portion of the Cassiopeia Milky Way, careful gradient control and moderate exposure lengths help keep both the cluster stars and the background field balanced.
Names and Catalog numbers
- C 10 (Caldwell 10)
- NGC 663
- Mel 11 (Melotte 11)
Position and the cosmic neighborhood
NGC 663 lies in northern Cassiopeia at a right ascension of 01h 46m 21s and a declination of +61° 12′ 42″, placing it deep within one of the richest sections of the northern Milky Way. From mid-northern latitudes this circumpolar region rides high overhead, making the cluster accessible for much of the year and ideal for long imaging sessions. It shares its stretch of sky with numerous other open clusters and nebulae scattered through Cassiopeia’s star clouds, so imagers can plan multi-target mosaics or panning sequences across the surrounding field. The dense background of faint Milky Way stars adds depth to any frame centered on this cluster.
Nice to Know
- The cluster carries several designations, appearing as Caldwell 10, Melotte 11, and NGC 663, so it turns up under multiple names in catalogs and planning software.
- At magnitude 7.1 it is a comparatively bright open cluster, well within reach of modest apertures and even capable binoculars under dark skies.
- Its physical diameter of about 33 light-years corresponds to an apparent size of 18′, offering a compact yet resolvable target that frames nicely in a single field.
- Situated some 6,370 light-years away in the Cassiopeia Milky Way, it is embedded in a star-dense region that makes for a striking photographic backdrop.
Brightness, distance and size
The object has an apparent magnitude of 7.1 mag, it lies about 6,370 light-years from Earth and spans roughly 33 light-years across. On the sky it appears about 18′ in size.
