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Aristyllus

Aristyllus ( ; fl. c. 261 BC) was a Greek astronomer, presumably of the school of Timocharis (c. 300 BC). He was among the earliest meridian-astronomy observers. Six of his stellar declinations are preserved in the Almagest (7.3). All are exactly correct within his over-cautious rounding to 1/4 degree. See discussion (and lessons) at DIO 7.1 ‡1 p. 13 (2007). Aristyllus was long mis-dated to c. 300 BC (which made his data look among the poorest of the ancients); but when his correct date was found by least-squares (Isis 73:259-265 [1982] p. 263), it was realized that his star declinations' accuracy was unexcelled in antiquity. His data suggest that he worked in Alexandria: see DIO 4.1 ‡3 Table 3 p. 45 (2004). A lunar crater, Aristillus, aptly near the Moon's meridian and at a lunar latitude roughly equal to the terrestrial latitude of Alexandria, is named after him.

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Article summary

Aristyllus ( ; fl. c. 261 BC) was a Greek astronomer, presumably of the school of Timocharis (c. 300 BC). He was among the earliest meridian-astronomy observers. Six of his stellar declinations are preserved in the Almagest (7.3). All are exactly correct within his over-cautious rounding to 1/4 degree. See discussion (and lessons) at DIO 7.1 ‡1 p. 13 (2007). Aristyllus was long mis-dated to c. 300 BC (which made his data look among the poorest of the ancients); but when his correct date was found by least-squares (Isis 73:259-265 [1982] p. 263), it was realized that his star declinations' accuracy was unexcelled in antiquity. His data suggest that he worked in Alexandria: see DIO 4.1 ‡3 Table 3 p. 45 (2004). A lunar crater, Aristillus, aptly near the Moon's meridian and at a lunar latitude roughly equal to the terrestrial latitude of Alexandria, is named after him.

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  1. Summarise the article in your own words. Which single claim would you verify first, and why?
  2. Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
  3. If two sources disagreed about one of these facts, what would you need in order to trust one over the other?

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