# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Astro*Dictionary by Michael Erlewine





2 articles for "Ptolemy"

Ptolemy [Astro*Index]

(tol-um-mee) (75-160?)

Greek astrologer and astronomer. Born Ptolemais Hermii (Latin name Claudius Ptolemaeus), he is usually called a Greek, although he may have been an Egyptian. He was not a member of the Egyptian royal family of Ptolemies. Some sources indicate that he stayed in Alexandria over a 40-year period, and that he lived to age 85. His major work was called Megale Mathematike Syntaxis (Great mathematical composition) or Megiste (Greatest) for many generations. After the fall of the Roman Empire, Ptolemy's writings were preserved by the Arabs, who called this work the Almagest. In 1175, the Arabic version was translated into Latin, influencing European thought during the Renaissance. He was, primarily, a compiler of the works of others, rather than an originator of new ideas. The Ptolemaic system of planetary motion, which is earth-centered, uses the epicycles and eccentrics of Hipparchus with a few refinements. He used a good approximation of the lunar distance from Hipparchus, but the poor value for the solar distance from Aristarchus. He chose the value of the earth's size given by Poseidonius, rather than that of Eratosthenes, thereby seriously affecting his geographical maps. He also wrote books on optics and geography, including carefully prepared maps and tables of longitude and latitude. When translated into Latin 1300 years later, these maps influenced the work of the map-maker Toscanelli, who provided Columbus with a map in 1481. Another large work, called the Tetrabiblos (Four Books) is devoted to astrology, and has influenced the development of astrology in the West from the 1st century to the present. Although he gives both the sign and degree of the Exaltations (Hypsomata) of the planets, he makes no attempt to explain the exact degrees; his explanation of the signs is not, at all, convincing. The true explanation of the origin of the Exaltations had to wait until modern times, when the Irish astrologer Cyril Fagan finally solved the mystery. Ptolemy advised using the Vernal Point as the fiducial (zero point) for the zodiac, assigning it the value ARI 00°, in accordance with the advice of Hipparchus. By this action, the Tropical Zodiac was born; it is still in use by most astrologers of the West, but was never accepted by the Hindu astrologers. This decision was at odds with other astrologers of his day, who placed the Vernal Point at ARI 10° or ARI 08°. Ptolemy attempts to justify his choice by means of arguments which are of a seasonal nature, and thus invalid if applied to individuals born in the Southern hemisphere. The ancient Sidereal Zodiac, which was fixed in reference to the stars, and the moving, modern Tropical Zodiac were nearly coincident during Ptolemy's lifetime; hence, no observational means was available which might have been used to distinguish between the two. On the subject of the Terms of the planets, in reference to their dominion of the Triplicities, Ptolemy notes that two systems then existed (Egyptian and Chaldean). Although drawn to the Chaldean system because of its schematic qualities, he advises that the Egyptian should be more relied upon. He then introduces a third scheme, taken from "an ancient writing which had fallen into his possession" which bears strong signs of typical Greek schematic manipulations.

See also: ♦ Dexter Aspect ♦ Equal House System ♦ Tetrabiblos
Ptolemy House System [Astro*Index]

Often confused with the Equal House System. Claudius Ptolemy proposed his method of House Division in Book 3, Chapter 12 ("The Prorogatory Places) of the Tetrabiblos. The primal division was taken from 5° above the Horizon to 25° below it; the 11th house ("The Good Daemon) was taken in dexter sextile thereto; the 30° in dexter quartile forming the `mid-heaven' above the earth (10th house); those in dexter trine making the 9th house (called God); and those in opposition belonging to the angle of the west (7th house).



Given that:
obl =+23.45°
LAT =+37.00°
ST=07:32:00 =113.00°


See also: ♦ Dexter Aspect ♦ Equal House System ♦ Tetrabiblos


Astro*Index Copyright © 1997 Michael Erlewine


[ TOP ]