**Astrology Notes - Herong's Notes** - v2.13, by Herong Yang

The Celestial Sphere

This section provides some basic knowledge of the celestial sphere.

The celestial sphere is an imaginary sphere of infinite radius centered on the Earth, on which all celestial bodies are assumed to be projected. Note that:

- The celestial sphere is an Earth-centered model of our universe.
- The celestial sphere is a 2-dimensional model where the 3-dimensional universe is projected to the surface of an imaginary sphere.
- Two coordinate systems are used for the surface of the celestial sphere: a fixed coordinate system and a relative coordinate system.

The following picture provides a good illustration of the celestial sphere, http://www.pfm.howard.edu:

The celestial sphere can be viewed as the sphere ceiling of the Earth where stars are located. Of course, this is not true, our view of stars from the Earth is a projection of stars located in a 3-dimensional space:

Table of Contents

Quick Introduction to Astrology

►Basics of Astrology and Astronomy

The Celestial Sphere Coordinate System

The Celestial Meridian and Zenith

The Precession - Rotation of Earth's Axis

Introduction to Western Zodiac Signs

Horoscope and Horoscopic Astrology