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Aristyllus

Flourished third century BCE

Aristyllus was an early astronomer in the school of Alexandria. Little is known about him. He made astronomical observations during the first half of the third century BCE, and was probably a pupil of Timocharis .

Aristyllus and Timocharis are usually considered to have compiled the first true catalog of the fixed stars, in which stars are identified by numerical measurements of their positions. (In earlier lists, stars had been identified by descriptions of their locations, typically with respect to other stars and constellations.) The catalog is not extant. Indeed, while Aristyllus and Timocharis certainly amassed a set of numerical observations of star positions, it is not, strictly speaking, known whether these observations were assembled into a catalog or table. Probably fewer than 100 stars were observed, and the positions were reputedly of low accuracy. Observations by Aristyllus or Timocharis survive in Ptolemy's Almagest for some 18