The Absolute Proper Motion of M3 and Its Galactic Orbit

We have obtained the absolute proper motion of globular cluster M3 from measurements of 14 plates taken with the 40cm refractor at Sheshan station of Shanghai observatory, spanning epoch is about 80 years.The positions and absolute proper motions of 24 stars in ACT catalogue are used as the reference frame.The reduction was made with the central overlapping principle.The absolute proper motions of 534 stars in the region of about 1°5×1°5 around the cluster M3 are determined.With the new data of proper motions, the membership probabilities of the stars are determined.The mean absolute proper motions for the cluster of-0.3±0.3 mas/yr in R.A.and-3.1±0.3 mas/yr in Dec.were obtained.Combining our results with the known distance and radial velocity of the cluster, we obtained its space motions and Galactic orbit s in two different three-component Galactic potentials.