Celestial sphere

The celestial sphere is an imaginary, any thin spherical shell with an infinitely large diameter or a direction or unit sphere that surrounds the geocentric celestial sphere the earth, as the topocentric observer. It serves as a mathematical calculation area for coordinates in astronomy and geodesy.

The celestial sphere is also called the celestial sphere, or firmament. This name derives from the ancient idea of the sphere: At one of the transparent spheres of heaven, the ancient astronomy thought " tacked " the heavenly bodies (Latin firmamentum, " fasteners "). As the oldest and most important sky illustration applies the Sky Disc of Nebra.

The position of the heavenly bodies with the aid of on the - specified celestial sphere to thinking Equatorial coordinate system - due to the Earth's rotation seemingly rotating. The celestial sphere has, if it is geocentric or is thought infinitely large, their poles in the extension of the Earth's axis. The line through these poles is called the celestial axis. The celestial equator is the projection corresponding to the Earth's equator to the ball. The axis of the topocentric celestial sphere is a parallel to the axis of the earth, the celestial equator is the parallel to the equatorial plane of the Earth plane through the observer location. Observed coordinates are always topocentric and may need to be converted into geocentric. The difference between the geocentric and topocentric celestial sphere is greater the closer the observed celestial body.