A sextant is an instrument for measuring the angle between two objects by bringing into coincidence to the eye of the observer, rays of light received directly from one object and reflected from the other. Its principal use is to measure the altitudes of celestial bodies above the visible sea horizon. Available in various types. When ordering, specify telescope (magnifying & lens diameter) and whether the sextant should be with or without illumination. Furnished with a wooden or plastic case.