Editing Axial precession (section)

===Middle Ages and Renaissance===
In [[Astronomy in medieval Islam|medieval Islamic astronomy]], precession was known based on Ptolemy's ''Almagest'', and by observations that refined the value.

[[Al-Battani]], in his work ''Zij Al-Sabi'', mentions Hipparchus's calculation of precession, and Ptolemy's value of 1 degree per 100 solar years, says that he measured precession and found it to be one degree per 66 solar years.<ref>{{Cite web
 |title=Zij Al-Sabi'
 |author=Al-Battani
 |url=http://shamela.ws/browse.php/book-452#page-132
 |access-date=30 September 2017
 |archive-url=https://web.archive.org/web/20170105192525/http://shamela.ws/browse.php/book-452#page-132
 |archive-date=5 January 2017
 |url-status=dead
 }}</ref>

Subsequently, [[Al-Sufi]], in his ''[[Book of Fixed Stars]]'', mentions the same values  that Ptolemy's value for precession is 1 degree per 100 solar years. He then quotes a different value from ''Zij Al Mumtahan'', which was done during [[Al-Ma'mun]]'s reign, of 1 degree for every 66 solar years. He also quotes the aforementioned ''Zij Al-Sabi'' of Al-Battani as adjusting coordinates for stars by 11 degrees and 10 minutes of arc to account for the difference between Al-Battani's time and Ptolemy's.<ref>
{{Cite web
 |title=Book of Fixed Stars
 |author=Al-Sufi
 |url=https://www.wdl.org/ar/item/18412/view/1/20/
}}</ref>

Later, the ''[[Zij-i Ilkhani]]'', compiled at the [[Maragheh observatory]], sets the precession of the equinoxes at 51 arc seconds per annum, which is very close to the modern value of 50.2 arc seconds.<ref>{{Cite journal |title=The Influence of Islamic Astronomy in Europe and the Far East |last=Rufus |first=W. C. |journal=Popular Astronomy |volume=47 |issue=5 |date=May 1939 |pages=233–238 [236] 
|bibcode = 1939PA.....47..233R}}.</ref>

In the Middle Ages, Islamic and Latin Christian astronomers treated "trepidation" as a motion of the fixed stars to be ''added to'' precession. This theory is commonly attributed to the [[Arab]] astronomer [[Thabit ibn Qurra]], but the attribution has been contested in modern times. [[Nicolaus Copernicus]] published a different account of trepidation in ''[[De revolutionibus orbium coelestium]]'' (1543). This work makes the first definite reference to precession as the result of a motion of the Earth's axis. Copernicus characterized precession as the third motion of the Earth.<ref>{{cite book |last=Gillispie |first=Charles Coulston |author-link=Charles Coulston Gillispie|title=The Edge of Objectivity: An Essay in the History of Scientific Ideas |year=1960 |publisher=Princeton University Press |isbn=0-691-02350-6 |url=https://archive.org/details/edgeofobjectivit00char |page=24}}</ref>