Celestial Equator

• The Celestial Equator is a Great Circle or disc that divides the Earth’s Sphere into exactly two Hemispheres.
• It is on precisely the same plane as the Equator.

Right Ascension

• The position of the Stars and Planets can then be determined by their angle relative to the Celestial Equator and this is known as Right Ascension.

First Point of Aries

• The First Point of Aries is where the Sun crosses the Celestial Equator at the Vernal Equinox.
• The Celestial Longitude of Stars and Planets in the Night Sky is measured by their angle relative to the Celestial Equator, and this is known as the Equatorial Coordinate System.

Equatorial Coordinate System

• The Equatorial Coordinate System is a method of determining the position of celestial objects by reference to the Celestial Equator and their angle from it measured by using Right Ascension.
• It differs from the Ecliptic Coordinate System which uses the Ecliptic to determine the position of celestial objects.