Epistolae of Gregory Chioniades, Athens 1906 edition by Trifon E. Evagelides. Gregory Choniades (Choniates, Chioniades) (died 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.