Differential rotation of the globular cluster omega Centauri has been
known for several decades already from radial velocity
observations. It has also been observed in differential proper
motions. In this seminar I will discuss the detection and
interpretation in the proper motion data, and the interpretation when
combined with the radial velocity data. In the processing of the
astrometric data, the Yale telescope used for the astrometric data was
reconstructed, to ensure that the observed effects could not be
contributed to changes in the objective mounting between the first and
second epoch exposures. Using simple models it is shown how the
rotation curves in radial velocity and proper motions translate into a
rotation axis and 3D rotation curve.