Abstract: An optical instrument has a low powered light point source mounted on a tube for orienting light point source along a predetermined viewing axis for one eye of an observer. An optical void surrounds the point light source, including the tube. The light point source is coherent and/or collimated so as to be substantially free of autokinesis effects. The tube is mounted on orientable support structure for the predetermined viewing axis for one eye of an observer whereby when said observer is viewing a scene through his other eye an optically fused image is presented to the observer with said predetermined viewing axis including the point in said scene wherein said point source appears.

Abstract: A surveying target having a housing with one open side, encloses a high intensity gas discharge flash tube. A light absorbing surface in the housing bounding the back and sides of said flash tube prevents reflection of light, thereby maintaining a relatively discrete outline. A light transparent cover member on said open side for passing light from said high intensity gas discharge tube toward an observer. A transmitter and receiver, and including resettable code devices are provided for limiting responsive operation only to transmitters transmitting a preassigned code and a corresponding receiver for detecting said preassigned code. A light transparent cover member filters light from said lamp of a predetermined wave length. A surveying system using an optical instrument for binocular visioned observers is also disclosed.