The term Actuator refers to a control motor, and the term is commonly used for telescopes to refer to such devices that physically position the telescope or parts of it. A motor to keep the telescope pointed at an object can go by that name. In large astronomical telescopes, smaller actuators may be used to align Segmented Mirrors to act as a single mirror or to position parts of an Adaptive Optics system. In a space telescope, the actuators may be positioning the attitude of the entire spacecraft.
Deformable Mirror (DM)