moving cluster

An open star cluster, the distance to which can be derived from measurements of the radial velocity and proper motion of individual members. The prime example is the Hyades. The members of the cluster are presumed to share a common motion through space. Perspective makes their paths appear to converge towards or diverge from a single point. The direction towards this point is parallel to the direction of motion of the stars. This provides sufficient information for the distance to be determined.