A physically related group of stars which share a common motion in space, such as the Hyades. Because of perspective, the proper motions appear to be directed towards a single point, called the convergent point. If the linear velocity of the cluster is known from observations of radial velocity, then the distance of each star can be estimated from the total proper motion; this technique is known as moving cluster parallax.

moving cluster:

As a result of perspective, a group of stars with a common motion away from us appear to be heading towards a convergent point.