DETERMINATION OF PROPER MOTIONS AND MEMBERSHIP OF THE OPEN CLUSTERS NGC-1750 AND NGC-1758

The kinematic state of the open clusters NGC 1750 and NGC 1758 has bee n studied using newly determined proper motions for 540 stars in a fie ld of 1.degrees 5 x 1.degrees 5 in the Taurus dark cloud region. The p roper motions are obtained from the reduction of PDS measurements of 2 0 plates that span a total time interval of 68 years, resulting in an average proper motion accuracy of 0.67 mas/yr. These proper motions ar e used to determine the membership probabilities of stars in the regio n by means of a new, improved method described in this paper. Of the 5 40 stars analyzed here, 332 are found to be probable members of NGC 17 50, and 23 are probable members of NGC 1758. The core radii of NGC 175 0 and NGC 1758 are determined to be 17.'2 and 2.'25 respectively.