Abstract: Apparatus for compensating for positioning, pointing and/or orientation errors caused by deflections of structural members and components of a high performance machine or device and/or for reducing vibration inputs to such machine or device and/or for micro-positioning such machine or device so as to improve the operational performance of such machine or device. The apparatus utilizes one or more active-type actuators, such as piezoelectric ceramic type actuators, which are arranged in a predetermined manner relative to the machine or device. A servo control device operating in accordance with a predetermined algorithm may be utilized for controlling the actuators or, alternatively, the apparatus may operate in an open loop manner.