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A diagram of a typical nautical sextant, a tool used in celestial navigation to measure the angle between two objects viewed by means of its optical sight. Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the ...
Sextant. A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation . The estimation of this angle, the altitude, is known as sighting or ...
Longitude by chronometer. Longitude by chronometer is a method, in navigation, of determining longitude using a marine chronometer, which was developed by John Harrison during the first half of the eighteenth century. It is an astronomical method of calculating the longitude at which a position line, drawn from a sight by sextant of any ...
A modern astrolabe made in Tabriz, Iran in 2013. An astrolabe ( Greek: ἀστρολάβος astrolábos, 'star-taker'; Arabic: ٱلأَسْطُرلاب al-Asṭurlāb; Persian: ستارهیاب Setāreyāb) is an astronomical instrument dating to ancient times. It serves as a star chart and physical model of visible heavenly bodies.
Sight reduction. In astronavigation, sight reduction is the process of deriving from a sight (in celestial navigation usually obtained using a sextant) the information needed for establishing a line of position, generally by intercept method . Sight is defined as the observation of the altitude, and sometimes also the azimuth, of a celestial ...
Navigators often use star charts to identify a star by its position relative to other stars. References like the Nautical Almanac and The American Practical Navigator provide four star charts, covering different portions of the celestial sphere. Two of these charts are azimuthal equidistant projections of the north and south poles. The other ...
Hawaiian navigators sailing multi-hulled canoe, c. 1781. Polynesian navigation or Polynesian wayfinding was used for thousands of years to enable long voyages across thousands of kilometres of the open Pacific Ocean. Polynesians made contact with nearly every island within the vast Polynesian Triangle, using outrigger canoes or double-hulled ...
Chronometer circa 1844-1860. A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies.