• synonyms

hour angle

noun Astronomy.
  1. the angle, measured westward through 360°, between the celestial meridian of an observer and the hour circle of a celestial body.
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Origin of hour angle

First recorded in 1830–40
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for hour angle

Historical Examples

  • Otherwise, the confusion of the azimuth with the hour-angle might cause a considerable error.

    Chaucer's Works, Volume 3 (of 7)

    Geoffrey Chaucer

British Dictionary definitions for hour angle

hour angle

  1. the angular distance along the celestial equator from the meridian of the observer to the hour circle of a particular celestial body
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

hour angle in Science

hour angle

  1. The angular distance, measured westward along the celestial equator, between the celestial meridian of the observer and the hour circle passing through a celestial body. A body's hour angle is measured in hours, minutes, and seconds, and corresponds to its right ascension as measured with respect to the observer's meridian (which changes with time) rather than the vernal equinox (which is fixed on the celestial equator). A celestial object that crossed the observer's meridian 3 hours and 20 minutes ago has an hour angle of +3 hours 20 minutes. An object that will not cross the meridian for another 3 hours and 20 minutes has an hour angle of -3 hours 20 minutes.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.