Ptolemy knew that Babylonian astronomers used mathematical schemes to “compute ” the times of past and future eclipses because they discovered that eclipses of the same character reoccur every 18 years. ​ — Almagest, IV, 2.
Ptolemy knew that Babylonian astronomers used mathematical schemes to “compute ” the times of past and future eclipses because they discovered that eclipses of the same character reoccur every 18 years. — Almagest, IV, 2. [ 1]