Abstract: A mounting system for mounting an optical element to a supporting unit of an optical system that may include several optical elements in a predetermined alignment with respect to one another and with respect to an optical axis. A carrier holding an optical element in a known position and orientation with respect to the carrier is attached to a supporting unit in a selected location and position of rotation, with respect to an axis that may be the optical axis, by a plurality of magnetic elements, ones of which are carried in or affixed to the supporting unit in predetermined locations and orientations, and other ones of which are included in or affixed to the carrier in predetermined locations and orientations that result in mutual attraction between corresponding ones of the magnetic elements when the carrier is in a predetermined position with respect to the supporting unit.