Horoscope, illustration of the position of the sun, moon, and planets from a given latitude and longitude on earth at a given moment, usually that of birth. The construction of the horoscope is based on the Ptolemaic system, in which the earth is stationary and the heavenly bodies move around it in fixed patterns. Astrologers have divided the heavens into 12 sections, each thought to be ruled by a different sign of the zodiac belt through which the sun, moon, and planets move in 12 fixed positions called houses. Once the particular sign and houses have been established, the mythological characteristics of the heavenly bodies, modified by the geometrical relationship between them, are used to foretell events in the life of the individual for whom the horoscope has been drawn. See also Astrology.