Timocharis

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Timocharis of Alexandria (

philosopher. Likely born in Alexandria, he was a contemporary of Euclid
.

Work

What little is known about Timocharis comes from citations by

arcminutes of the star η Virginis.[4]

The observations by Timocharis are among the oldest

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.[citation needed
]

He is regarded as the first astronomer to have made a recorded mention of the planet Mercury.[7][8]

The crater Timocharis on the Moon is named after him.[9]

References

  1. doi:10.1093/mnras/169.2.331
    .
  2. ISBN 0-87169-233-3
    .
  3. ^ Jones, A. (1997), On the reconstructed Macedonian and Egyptian lunar calendars (PDF), vol. 119, pp. 157–166, retrieved 2009-09-10
  4. ISBN 0-8493-4483-2
    .
  5. ^
    ISBN 0-19-509539-1
    .
  6. ISBN 0-486-27740-2
    .
  7. ^ "intro". history.nasa.gov. Retrieved 2016-04-22.
  8. ISBN 9780521867115
    .
  9. ^ "Timocharis". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
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