A lithographic apparatus comprises a projection system comprising position sensors to measure a position of optical elements of the projection system. The positions sensors are referenced to a sensor frame. Damping actuators damp vibrations of the sensor frame. A control device drives the actuators and is configured to derive sensor frame damping force signals from at least one of the acceleration signals and the sensor frame position signals, derive an estimated line of sight error from the position signals, determine actuator drive signals from the sensor frame damping force signals and the estimated line of sight error, drive the actuators using the actuator drive signals to dampen the sensor frame and to at least partly compensate the estimated line of sight error.