Star-Cluster Astrometry with Ground-Based Wide Field Imagers
  We show the astrometric potential of the Wide Field Imager at the focus of the MPI-ESO 2.2m Telescope. Currently, we are able to measure the position of a well-exposed star with a precision of $\sim$4 mas/frame in each coordinate (under 0.8 arcsec seeing conditions). We present some preliminary results here. 
L. R. Bedin (1), J. Anderson (2), G. Piotto (3), Y. Momany (3), R. S.   Yadav (3) ((1) E.S.O. Garching, (2) Rice Univ. Houst...