Abstract

An improved sextant which provides a very accurate angular measurement of the position of a celestial body relative to the horizon. The sextant is a typical prior art sextant having a horizon glass and an index mirror, and wherein the sextant is sighted by adjusting the angular position of the index mirror to align an image of the celestial body with a sighting of the horizon. An angular position encoder is coupled to the index mirror to provide a digital electrical output signal indicative of the exact angular position of the index mirror. The sextant includes an electrical clock for producing an electrical output signal which indicates the exact time the sighting is taken. The sextant includes electronics for automatically synchronizing the electrical output signal from the encoder with the electrical output signal from the clock. The electrical output signals are in a form suitable for further electrical processing and automatic data reduction to automatically and simultaneously provide the navigator with a final positional output once he has taken several sightings.The sextant may be operated in any one of the three modes. The first mode allows an instantaneous sight to be taken, and the sextant provides an instantaneous readout of the encoder and the clock. In a second mode, an averaged sighting is made automatically. In a third mode, the clock within the sextant is utilized solely as a chronometer.