A circle or belt that was thought to stretch 8 degrees on either side of the ecliptic in ancient times (q.v.). Because of the great latitudes that Venus and Mars reach, modern astronomers have expanded it to 9 degrees on either side. A perpendicular to the ecliptic is used to determine the location of any planet or star within or outside of the zodiac. The geocentric longitude of a star or planet is the point where this perpendicular intersects the ecliptic. In some ways, the zodiac and the ecliptic are the same thing because they both start at the Vernal Equinox. The Celestial Sphere is the fifth of the seven celestial spheres.