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Azimuth Compass

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Navigational instrument.

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The Azimuth compass differed from the ordinary sea compass in that the circumference of the card was divided into degrees. On top of the compass housing was a straight flat metal bar with two upright sight-vanes on either end. Each vane had a vertical slit, down the centre of which a small string or wire was stretched to improve accuracy in sighting.

Housed in a box, the azimuth compass was carried to the best observation site on a vessel, and the sight vanes moved until they were aligned with the sun, the moon or the pole star. In the case of the sun, the sight vanes were moved until the shadow of the string or wire fell along the middle of the index. When the moon (or pole star) was the object of observation, the vanes were moved until it was aligned with the two strings.

By this method a reading for north was obtained from the azimuth compass and then compared with that found using the ordinary sea compass. The variation was applied to the magnetic course shown by the Mariner’s Compass, and thus the true course with respect to the meridian was discovered.

 
Related Entries for Azimuth Compass
Concepts: Azimuth | Compass Variation
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Online Sources
  • Falconer, William, Online edition of William Falconer's Universal Dictionary of the Marine, or, a Copious Explanation of the Technical Terms and Phrases employed in the Construction, ...of a Ship...derived from the text of the London 1780 edition published by Thomas Cadell, 2004 edn, South Seas, http://southseas.nla.gov.au/refs/falc/contents.html. [ Details ]

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Prepared by: Turnbull, P
Created: 4 October 2001
Modified: 29 August 2002

Published by South Seas, 1 February 2004
Comments, questions, corrections and additions: Paul.Turnbull@jcu.edu.au
Prepared by: Paul Turnbull
Updated: 28 June 2004
To cite this page use: http://nla.gov.au/nla.cs-ss-biogs-P000052

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