::Celestial sphere


Sphere::books    System::earth    Objects::first    Geometry::title    Stars::earth's    Ecliptic::position


The Earth rotating within a relatively small-diameter Earth-centered celestial sphere. Depicted here are stars (white), the ecliptic (red), and lines of right ascension and declination (green) of the equatorial coordinate system.

In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with Earth. All objects in the observer's sky can be thought of as projected upon the inside surface of the celestial sphere, as if it were the underside of a dome or a hemispherical screen. The celestial sphere is a practical tool for spherical astronomy, allowing observers to plot positions of objects in the sky when their distances are unknown or unimportant.

Celestial sphere sections
Intro  Introduction  Celestial coordinate systems  History  Star globe  Bodies other than Earth  See also  Notes  References  External links  

PREVIOUS: IntroNEXT: Introduction