Actuator for a device for the rotary positioning of a movable element for space equipment comprising a part attached to the fixed portion of said equipment, a bearing, a sleeve designed to actuate the movable portion of said equipment and mounted on an output shaft supported by a first race of said bearing, said actuator comprising a mechanically movable input means and being capable of converting a movement of the input means into a rotary movement of the output shaft about the axis of said bearing, characterized in that said second race of said bearing is connected in rotation to the part of said equipment, in that an adjustable stop so as to angularly limit the relative rotation of the two races of the bearing, and in that the rate of rotation of the output shaft in response to a movement of the input means is different depending on whether or not the sleeve is resting on the adjustable stop.