#### 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.