Celestial Navigation

Celestial navigation systems are based on observation of the positions of the Sun, Moon and stars. By knowing which point on the rotating earth a celestial object is currently above and measuring its height above the observer's horizon, the navigator can determine his distance from that subpoint. A Nautical almanac and a chronometer are used to compute the subpoint on earth a celestial body is over, and a sextant is used to measure the body's angular height above the horizon. That height can then be used to compute ones distance from the subpoint to create a circular line of position. A navigator shoots a number of stars in succession to give a series of overlapping lines of position. Where they intersect is his celestial fix. The moon and sun may also be used. The sun can also be used by itself to shoot a succession of lines of position (best done around local noon) to determine a position as well.