Abstract
We show that a simple modification to an optical table with pneumatic vibration isolation can be used to actively reduce the long term drift in the tilt of the table by nearly a factor of 1000. Without active stabilization, we measure a root-mean-square (rms) tilt variation of 270 mu rad over three days. The active stabilization can be used to limit the tilt to 0.35 mu rad rms over the same time period. This technique can be used to minimize drift in tilt-sensitive experiments.