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Timocharis of Alexandria (Greek: Τιμόχαρις or Τιμοχάρης, gen. Τιμοχάρους; c. 320–260 BC) was a Greek astronomer and philosopher. Likely born in Alexandria, he was a contemporary of Euclid.

Work

What little is known about Timocharis comes from citations by Ptolemy in the Almagest. These indicate that Timocharis worked in Alexandria during the 290s and 280s BC. Ptolemy lists the declination of 18 stars as recorded by Timocharis or Aristillus in roughly the year 290 BC.[1] Between 295 and 272 BC, Timocharis recorded four lunar occultations and the passage of the planet Venus across a star.[2] These were recorded using both the Egyptian and Athenian calendars.[3] The observed stellar passage by Venus may have occurred on October 12, 272 BC when the planet came within 15 arcminutes of the star η Virginis.[4]

The observations by Timocharis are among the oldest Greek records that can be assigned a specific date. They are only exceeded by records of the summer solstice of 432 BC, as noted by Euctemon and Meton.[5] Timocharis worked with Aristillus in an astronomical observatory that was most likely part of the Library of Alexandria. Their equipment would have been simple, most likely consisting of gnomons, sundials and an armillary sphere. The two were contemporaries of Aristarchus of Samos, but it is unclear whether there was any association between Timocharis and Aristarchus.[6]

During his astronomical observations, Timocharis recorded that the star Spica was located 8° west of the Autumnal equinox. Later, Hipparchus observed that Spica was only 6° west of the Autumnal equinox. Hipparchus was able to deduce the period during which Timocharis made his observations based upon the records of earlier lunar eclipses. From this difference, Hipparchus discovered that the longitudes of the stars had changed over time, which led him to determine the first value of the precession of the equinoxes as no less than 1/100° per year.[5]

In approximately 3rd century BC, with the help of Aristillus, he created the first star catalogue in the Western world.

Andronicus of Cyrrhus or Andronicus Cyrrhestes (Greek: Ἀνδρόνικος Κυρρήστου, Andrónikos Kyrrhēstou), son of Hermias, was a Macedonian astronomer who flourished about 100 BC.
Contents

Life

He built a horologion at Athens, the so-called Tower of the Winds, a considerable portion of which still exists. It is octagonal, with figures carved on each side, representing the eight principal winds.[1] In antiquity a bronze figure of Triton on the summit, with a rod in his hand, turned round by the wind, pointed to the quarter from which it blew. From this model is derived the custom of placing weather cocks on steeples.[2]
Notes

Joseph V. Noble; Derek J. de Solla Price: The Water Clock in the Tower of the Winds, American Journal of Archaeology, Vol. 72, No. 4 (1968), p353.

Chisholm 1911, p. 23.

References

This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Andronicus of Cyrrhus". Encyclopædia Britannica. 1 (11th ed.). Cambridge University Press. p. 976.

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Ancient Greek astronomy
Astronomers

Aglaonice Agrippa Anaximander Andronicus Apollonius Aratus Aristarchus Aristyllus Attalus Autolycus Bion Callippus Cleomedes Cleostratus Conon Eratosthenes Euctemon Eudoxus Geminus Heraclides Hicetas Hipparchus Hippocrates of Chios Hypsicles Menelaus Meton Oenopides Philip of Opus Philolaus Posidonius Ptolemy Pytheas Seleucus Sosigenes of Alexandria Sosigenes the Peripatetic Strabo Thales Theodosius Theon of Alexandria Theon of Smyrna Timocharis

Works

Almagest (Ptolemy) On Sizes and Distances (Hipparchus) On the Sizes and Distances (Aristarchus) On the Heavens (Aristotle)

Instruments

Antikythera mechanism Armillary sphere Astrolabe Dioptra Equatorial ring Gnomon Mural instrument Triquetrum

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Callippic cycle Celestial spheres Circle of latitude Counter-Earth Deferent and epicycle Equant Geocentrism Heliocentrism Hipparchic cycle Metonic cycle Octaeteris Solstice Spherical Earth Sublunary sphere Zodiac

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