sextant for precise navigation - has camera attached to photograph image of sun with time from chronometer

摘要

A sextant for navigation requires that the navigator operates the instrument at the same time as the time is obtained from a chronometer. This problem is overcome by photographing the image from the sextant together with the chronometer reading. A supplementary lens (14) is located adjacent to the sight glass (5) of a sextant in order to divide the beam into two parts. One part (15) is observed by the navigater and the second part is directed at right angles towards a sensitive plate (17) in a photographic instrument (18). The plate is rapidly developed in the camera and includes a scale graduated in fractions of the sun's diameter. This allows the navigator to determine the angle if the sun's image is not on the horizon line. The chronometer time is included on the photograph.