In the Almagest Ptolemy describes a meridian circle which consisted of a fixed graduated outer ring and a movable inner ring with tabs that used a shadow to set the Sun's position.
Almagest |
The prevailing astronomical model of the cosmos in Europe in the 1,400 years leading up to the 16th century was that created by the Roman citizen Claudius Ptolemy in his Almagest, dating from about 150 A.D. Throughout the Middle Ages it was spoken of as the authoritative text on astronomy, although its author remained a little understood figure frequently mistaken as one of the Ptolemaic rulers of Egypt.
Having heard of Flamsteed's astronomical proficiency, Halton called to see him at Derby in 1666, and afterwards sent him Giovanni Battista Riccioli's New Almagest, Johannes Kepler's Rudolphine Tables, and other books on astronomy.
During the Renaissance, the work was attributed to the Roman historian Gaius Julius Hyginus who lived during the 1st century BC However, the fact that the book lists most of the constellations north of the ecliptic in the same order as Ptolemy's Almagest (written in the 2nd century AD) has led many to believe that a more recent Hyginus created the text.