an imaginary sphere of infinite extent on which all celestial objects appear to lie: the observer is always at its center
An imaginary sphere of infinite extent with the earth at its center and on which the stars, planets, and other heavenly bodies appear to be located.
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
- Alternative spelling of celestial sphere.