Dr. Cudworth's star cluster research at the Yerkes Observatory primarily involves observational investigations of proper motions and photometric studies of the members of globular and open clusters. Star clusters are important for testing theories of stellar evolution, galactic evolution, and stellar dynamics. Clusters also contribute to the luminosity calibration for a variety of types of stars, as well as the distance scale of the Galaxy and the Universe. In all of these areas a criterion for membership of stars in the cluster is needed which is independent of theories of stellar evolution. measurements of proper motions are used to derive cluster membership, study the internal dynamics of the clusters, and derive the cluster space velocities. Dr. Cudworth has a reputation for careful and accurate contributions in this area of fundamental astronomy.
