Q825894

NGC 663 image using PlaneWave CDK 12.5" telescope from Talent, OR NGC 663 (also known as Caldwell 10) is a young open cluster located 8,800 light years from Earth in the constellation of Cassiopeia. It has an estimated 400 stars and spans about a quarter of a degree across the sky. It can reportedly be detected with the unaided eye, although a telescope is recommended for best viewing. The brightest members of the cluster can be viewed with binoculars. Although the listed visual magnitude is 7.1, several observers have reported higher estimates.

Based on its parallax as measured by Gaia, it is located about 2,700 parsecs distant with an estimated age of 20–25 million years. This means that stars of spectral class B2 or higher (in the sense of higher mass), are reaching the end of their main sequence lifespan. This cluster appears to be located in front of a molecular cloud, although the two are not physically associated. This cloud has the effect of blocking background stars from the visual image of the cluster as it lies at a distance of 300 parsecs.