celestial sphere definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
an imaginary sphere of infinite extent on which all celestial objects appear to lie: the observer is always at its center
celestial sphere definition by American Heritage Dictionary
nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
An imaginary sphere of infinite extent with the earth at its center on which the stars, planets, and other heavenly bodies appear to be located.
celestial sphere - Science Definition
An imaginary sphere with Earth at its center. The stars, planets, Sun, Moon, and other celestial bodies appear to be located on this sphere, and the sphere appears to rotate around the Earth's extended axis once every 24 hours, carrying the celestial bodies with it overhead and giving them their diurnal motions. The celestial sphere is essentially a spherical map of the sky that provides the basis for the coordinate systems used in celestial navigation and in specifying the positions and motions of celestial objects. See more at altazimuth coordinate system, ecliptic coordinate system, equatorial coordinate system.