Gregory Choniades

Gregory Choniades (also Choniates, Chioniades; Greek: Γρηγόριος Χιονιάδης; c. 1240 – 1320) was a Byzantine Greek astronomer. He travelled to Persia where he learnt Persian mathematical and astronomical science which he introduced into Byzantium upon return from Persia and founded an astronomical academy at Trebizond. Choniades also served as Orthodox Bishop in Tabriz.

Information about Choniades survives from some contemporary sources. In 1347, George Chrysokokkes writes that "a certain Chioniades, who had been raised in Constantinople, fell in love with mathematics and other sciences. After he had mastered medicine, he wished to study astronomy; he was informed that, in order to satisfy his desire, he would have to go to Persia. He traveled to Trebizond, where he was given some assistance by the Emperor Alexios II of Trebizond, and thence proceeded to Persia itself, where he persuaded yet another Emperor to aid him. He eventually learned all that he wished to know, and returned to Trebizond, bearing away from Persia a number of astronomical texts which he translated into Greek."

Sixteen of Choniades' letters have survived, which confirm that he received assistance from Alexios II and traveled to Persia. Choniades translated a number of Arabic and Persian works on mathematics and astronomy, including the astronomical tables of his teacher Shams al-Din al-Bukhari, who had worked at the famous Maragheh observatory under the polymath Nasir al-Din al-Tusi. Choniades played an important role in transmitting several innovations from the Islamic world to Europe. These include the introduction of the universal latitude-independent astrolabe to Europe and a Greek description of the Tusi-couple, which would later have an influence on Copernican heliocentrism. Choniades also translated several Zij treatises into Greek, including the Persian Zij-i Ilkhani by al-Tusi and the Maragheh observatory as well as the Seljuk Sanjaric Tables by Al-Khazini, an Islamic astronomer of Byzantine Greek descent.

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