A mount for a telescope or other optical instrument comprising: a base; a holder for supporting an optical instrument mounted thereto; a worm gear assembly; the holder movable relative to the base about a wheel axis (18, 112) by operation of the worm gear assembly; the worm gear assembly comprising: a worm wheel rigidly connected to the holder, such that movement of the worm wheel about the wheel axis causes corresponding movement of the holder about the wheel axis; a worm shaft comprising a worm body extending in a longitudinal direction and a thread extending in a spiral on the worm body around a worm axis that extends in the longitudinal direction and is orthogonal to the wheel axis, the worm shaft supported by the base for rotational movement about the worm axis; the worm wheel comprising a generally disc-shaped wheel body comprising a plurality of radially extending and circumferentially spaced apart teeth at a radially outermost peripheral surface for engaging the thread of the worm shaft, so that rotation of the worm shaft about the worm axis causes, by engagement of the teeth and the thread, corresponding rotation of the worm wheel about the wheel axis and corresponding relative rotation of the holder and the base about the wheel axis; characterized in that the wheel body is shaped to define a plurality of elasticity-enhancing cutouts spaced apart from the wheel axis and extending through the wheel body in directions parallel to the wheel axis, the elasticity-enhancing cutouts enhancing elasticity of the worm wheel in a radial direction relative to a solid wheel body such that the worm wheel can deform radially and inwardly. a base; a holder for supporting an optical instrument mounted thereto; a worm gear assembly; the holder movable relative to the base about a wheel axis (18, 112) by operation of the worm gear assembly; the worm gear assembly comprising: a worm wheel rigidly connected to the holder, such that movement of the worm wheel about the wheel axis causes corresponding movement of the holder about the wheel axis; a worm shaft comprising a worm body extending in a longitudinal direction and a thread extending in a spiral on the worm body around a worm axis that extends in the longitudinal direction and is orthogonal to the wheel axis, the worm shaft supported by the base for rotational movement about the worm axis; the worm wheel comprising a generally disc-shaped wheel body comprising a plurality of radially extending and circumferentially spaced apart teeth at a radially outermost peripheral surface for engaging the thread of the worm shaft, so that rotation of the worm shaft about the worm axis causes, by engagement of the teeth and the thread, corresponding rotation of the worm wheel about the wheel axis and corresponding relative rotation of the holder and the base about the wheel axis; characterized in that the wheel body is shaped to define a plurality of elasticity-enhancing cutouts spaced apart from the wheel axis and extending through the wheel body in directions parallel to the wheel axis, the elasticity-enhancing cutouts enhancing elasticity of the worm wheel in a radial direction relative to a solid wheel body such that the worm wheel can deform radially and inwardly. a worm wheel rigidly connected to the holder, such that movement of the worm wheel about the wheel axis causes corresponding movement of the holder about the wheel axis; a worm shaft comprising a worm body extending in a longitudinal direction and a thread extending in a spiral on the worm body around a worm axis that extends in the longitudinal direction and is orthogonal to the wheel axis, the worm shaft supported by the base for rotational movement about the worm axis; the worm wheel comprising a generally disc-shaped wheel body comprising a plurality of radially extending and circumferentially spaced apart teeth at a radially outermost peripheral surface for engaging the thread of the worm shaft, so that rotation of the worm shaft about the worm axis causes, by engagement of the teeth and the thread, corresponding rotation of the worm wheel about the wheel axis and corresponding relative rotation of the holder and the base about the wheel axis; characterized in that the wheel body is shaped to define a plurality of elasticity-enhancing cutouts spaced apart from the wheel axis and extending through the wheel body in directions parallel to the wheel axis, the elasticity-enhancing cutouts enhancing elasticity of the worm wheel in a radial direction relative to a solid wheel body such that the worm wheel can deform radially and inwardly.