celestial coordinate system

Imaginary horizontal and vertical lines used to describe the position of an object on the celestial sphere.

North celestial pole

Projection of the North terrestrial pole onto the celestial sphere.

declination

One of two coordinates used to locate a celestial body on the celestial sphere; similar to terrestrial latitude.

ecliptic

Projection of the Sun’s apparent annual path onto the celestial sphere.

right ascension

One of two coordinates used to locate a celestial body on the celestial sphere; similar to terrestrial longitude.

celestial meridian

Projection of a terrestrial meridian onto the celestial sphere.

celestial sphere

Imaginary sphere where celestial bodies are observed and positioned.

celestial equator

Projection of the terrestrial Equator onto the celestial sphere; serves as the point of origin for declinations.

terrestrial sphere

Shape of Earth whose coordinates are projected onto the celestial sphere.

vernal equinox

Point at which the ecliptic and the celestial equator intersect; serves as the point of origin for right ascensions.

South celestial pole

Projection of the South terrestrial pole onto the celestial sphere.

Equator

Imaginary circle surrounding Earth at its widest circumference, dividing it into two hemispheres: the Northern hemisphere and the Southern hemisphere.

inclination

Angle formed between an imaginary line connecting the terrestrial poles and an imaginary line perpendicular to the ecliptic.