Celestial Navigation

Information about Celestial Navigation

Published on November 14, 2007

Author: Estelle

Source: authorstream.com

Content

Celestial Navigation:  Celestial Navigation By David Mackie What is Celestial Navigation?:  What is Celestial Navigation? It is the art and science of finding one's geographic position by means of astronomical observations, particularly by measuring altitudes of celestial objects – sun, moon, planets, or stars. Why?:  Why? For sailors to voyage away from land they needed some way so not to get lost Sea is featureless and has no ‘land’marks or signs for directions to be given by Even though they had compasses… they needed an accurate way of locating their position The Phoenicians :  The Phoenicians By day: The location of sunrise and sunset divided sky into 2 areas East & West called Asu (sunrise) and Ereb (sunset) [Asia & Europe] By night: At any 1 time in the year & place, stars where a certain “height” above see, measurable by finger widths Little Bear:  Little Bear Philosopher Thales of Miletos taught Ionian sailors to navigate by the Little Bear constellation fully 600 years before the birth of Christ. Position on Earth:  Position on Earth Latitude: The lines that run east and west, parallel to the equator. Longitude: The lines that run north and south. The line that passes through Greenwich, England is called the Prime Meridian. You need both of these to give your position on the face of the earth. Direction - The Compass:  Direction - The Compass Chinese knew about the powers of magnetism as early as the 3rd millennium B.C Only seen early present millennium for sea navigation Took a long time to come into wide use, as many seamen thought it operated by black magic Determining Latitude:  Determining Latitude A vessel's latitude was easily found by observing the height of the noon sun In the northern hemisphere, navigators can used the North Star as a way to determine their latitude. The angle that the North Star is above the horizon is equal to the latitude of the observer. Devices for determining Latitude:  Devices for determining Latitude Determining Latitude - Sextant:  Determining Latitude - Sextant Invented in 1731 It was the most advanced of these devices Determine their latitude to within a sea mile even from a swaying deck. Determining Longitude:  Determining Longitude Finding longitude remained a mystery for a long time Early part of 17-hundreds a Royal Committee offered a prize of £20,000 to the person who could determine longitude at sea. $$$ Earth rotates 15 degrees every hour (360/24) If you know the precise time at the prime meridian of longitude, the difference between that time and the navigator's local time (measured at high noon) will give him his longitude. Some ideas put forward:  Some ideas put forward Magnetic Variation Time Signals massive fleet of vessels luminous cannon shot at a predetermined time each day Cost & Impracticality Moons Of Jupiter  Galileo suggestion to determine precise time idea actually worked but pitching vessel made observations impractical. Lunar Distance Measured the angle between the moon and other celestial bodies to determine precise time. calculations were difficult and awkward, taking up to 4 hours Wounded Dogs to determine Longitude:  Wounded Dogs to determine Longitude mysterious substance called "powder of sympathy" if rubbed on a bandage taken from a wounded dog would cause the dog to howl in pain Even if the dog were hundreds of miles away from the bandage. If done in England at a predetermined time every day, then the dog's howling would give the navigator a daily time signal. extended journeys - dog would have to be re-injured to keep the wound fresh. Luckily for the dogs, this scheme didn't pan out. The idea that worked :  The idea that worked  Chronometer John Harrison - British clockmaker in 1728 a clock which was consistently accurate at sea. At last the mariner had the ability to easily and consistently determine his exact position. Finding the South Celestial Pole using the Southern Cross:  Finding the South Celestial Pole using the Southern Cross Questions?:  Questions?

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