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  2. Longitude by chronometer - Wikipedia

    en.wikipedia.org/wiki/Longitude_by_chronometer

    The Sextant reading is known as the 'Sextant Altitude'. This is corrected by use of tables to a 'True Altitude'. The actual declination and hour angle of the celestial body are found from astronomical tables for the time of the measurement and together with the 'True Altitude' are put into a formula with the assumed latitude.

  3. Celestial navigation - Wikipedia

    en.wikipedia.org/wiki/Celestial_navigation

    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 ...

  4. Sextant - Wikipedia

    en.wikipedia.org/wiki/Sextant

    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 ...

  5. Meridian altitude - Wikipedia

    en.wikipedia.org/wiki/Meridian_altitude

    Meridian altitude is the simplest calculation of celestial navigation, in which an observer determines his latitude by measuring the altitude of an astronomical object at the time of its meridian contact. A meridian contact is the moment when the object contacts the observer's meridian, i.e. the imaginary line running north–south and through ...

  6. Sight reduction - Wikipedia

    en.wikipedia.org/wiki/Sight_reduction

    Sight is defined as the observation of the altitude, and sometimes also the azimuth, of a celestial body for a line of position; or the data obtained by such observation. [1] The mathematical basis of sight reduction is the circle of equal altitude. The calculation can be done by computer, or by hand via tabular methods and longhand methods.

  7. Navigational triangle - Wikipedia

    en.wikipedia.org/wiki/Navigational_triangle

    Finding the latitude requires measuring the vertical angle (altitude) of X from the horizon using a sextant, the declination of X from a reference book, and a set of sight reduction Tables. The sun, moon, and planets move relative to the celestial sphere, but only the stars' hour angles change with the rotation of the earth, completing a full ...

  8. Intercept method - Wikipedia

    en.wikipedia.org/wiki/Intercept_method

    Intercept method. In astronomical navigation, the intercept method, also known as Marcq St. Hilaire method, is a method of calculating an observer's position on Earth ( geopositioning ). It was originally called the azimuth intercept method because the process involves drawing a line which intercepts the azimuth line.

  9. Wikipedia : Featured picture candidates/Using the sextant

    en.wikipedia.org/wiki/Wikipedia:Featured_picture...

    Voilà, the new version of the sextant is ready. The animation is now smoother and a bit simplified. I decided to include the light rays only at the begining and at the end, otherwise the image would be too cluttered. But the sextant is a working replica, i.e., the angles and reflections are all correct. - Alvesgaspar 21:34, 1 November 2006 (UTC)