An actuator for an optic mount in a vacuum environment includes a bellows around an actuator compartment. The bellows provides a seal around the actuator. A filter assembly is positioned between the actuator compartment and an interior of a vacuum chamber. The filter assembly includes a first particle filter, a second particle filter, and a purifier medium between the first particle filter and the second particle filter. Vacuum conditions in the actuator compartment can be achieved with a pump for the vacuum chamber, but particles and contaminants from the actuator or actuator compartment are captured by the filter assembly.