The Almagest was Ptolemy’s first and most ambitious work.
Written in about 147 A.D., it is a 13 volume set of books that attempted to include all the astronomical knowledge available at the time.
Its main goal was to allow people to calculate the positions of all celestial bodies the Sun, the Moon, planets, and stars, for any time.
What is most admirable about the Almagest is that it gathered in one work all knowledge of mathematics and astronomy available at Ptolemy’s time. He added to this history his own studies and theories.
It is the first complete book on astronomy that is still in existence.
The Almagest’s other strength is that its system for predicting future planetary positions was very accurate.
Ptolemy had researched astronomical records taken as far back as 721 B.C. in Babylon. He relied heavily on the records of the famous Greek astronomer Hipparchus, who observed the stars and planets daily from 147 to 127 B.C.
Ptolemy also personally observed their movements from A.D. 125 to 141.
Ptolemy’s 13-volume Algamest was the standard astronomical reference for more than 1,000 years.
Ptolemy is often depicted as wearing a crown, sitting next to an armillary sphere, an astronomical instrument.
The Latin translator, Regiomontanus, is usually seated on the right.
The word Almagest is the Latin form of the Arabic name الكتاب المجسطي, (al-kitabu-l-mijisti), and means “the Great Compilation”.