Almagestu

Almagest is a comprehensive treatise on astronomy written in Greek by Claudius Ptolemy in the 2nd century CE. The work is traditionally titled in English after the Latinized Arabic name Almagest, itself derived from al-Majist or al-Majisti. The original Greek title is often associated with the mathematical treatise known as the Mathemata Syntaxis, and the Almagest became the standard reference for classical astronomy in later periods.

The text is organized into 13 books and presents a complete program of mathematical astronomy. It systematizes the geocentric model of the cosmos, explaining planetary motions with deferents and epicycles, and introducing the concept of the equant to account for irregular orbital speeds. It covers the motions of the Sun, Moon, and five known planets, and includes methods for predicting celestial positions, solar and lunar eclipses, and other phenomena. The work also contains extensive tables, including trigonometric data and the Table of Chords.

A notable feature of the Almagest is its star catalog, which lists about 1,022 fixed stars with their positions relative to the zodiac. The catalog synthesizes earlier Greek and Babylonian observations and remains a foundational reference for medieval and early modern astronomy.

Influence and transmission: the Almagest dominated tanto Islamic and European astronomy for more than a millennium. It was translated into Arabic during the medieval period and subsequently into Latin in the 12th century, profoundly shaping astronomical thought until the Copernican revolution. Today it is regarded as one of the most important scientific treatises of antiquity.