Abstract: An optical measuring instrument permits the user to adapt the handle position optimally to his individual wishes and habits while holding the instrument. An adapter is fixed to the limbus body. The adapter includes curved slots for accepting fixing screws that lie within bores of the head part of the handle. By loosening the screws, one may adjust the position of the handle through a preselected angular range, tightening the screws to fix a preferred handle position.

Abstract: A manually-rotatable switch knob is provided on the alhidade of a sextant that is connected to a switching pin of hardened steel arranged eccentrically to the mounting of the knob. The switching pin engages the drum-screw mounting and, under the action of a stop spring, permits the drum screw to be switched back and forth between two stable stop locations when the knob is rotated. In the one stop location, the drum screw engages the limbus toothing. In the other location, the drum screw is completely disengaged from the limbus toothing so that the alhidade can be freely pivoted without risk of the drum screw damaging the limbus toothing during the movement of the alhidade. The stop spring also produces precisely defined contact pressure between the drum screw and the limbus toothing. The previously possible introduction of bending moments into the alhidade during rough adjustment is eliminated.