HST PROPER MOTIONS IN GLOBULAR CLUSTERS

Thanks to its resolving power, exquisite calibration, and ever-growing time baseline, 
HST is able to measure proper motions of individual stars within globular clusters.  
For the nearest clusters, we can measure motions of individual stars well down the 
main sequence to better than 0.1 mas/yr (2 km/s), even in the most crowded cluster 
cores.  This allows an unprecedented array of constraints on dynamical models:  we 
can search for central massive objects, measure the anisotropy of stellar motions 
directly, determine whether equipartition is present in the motions of stars of 
different mass, and search for differences in kinematics between different stellar 
populations.  I will begin with an overview of the motions we measured at the center of 
Omega Cen and will compare the results with those from recent radial-velocity studies.  
I will then present some early results of proper motions at the centers of three clusters: 
NGC2808, NGC6341 (M92), and NGC6752.   There are many more clusters to come.