High precision measurements of the celestial coordinates of pulsars are reviewed. The determination of annual parallaxes and proper motions with VLBI techniques is illustrated for the cases of PSR 1929+10 and PSR 0950+08. Pulsar astrometry can be expected to yield important information on the relative orientations of fundamental reference frames. In particular, pulse timing observations yield positions in a reference frame based on motions of the planets, while interferometric position measurements are based on an Earth-equatorial system.
VLBI and Compact Radio Sources
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