Asada Goryu (1734–1799) was a Japanese astronomer who was instrumental in turning Japanese astronomy and calendrical science away from the traditional Chinese style and toward Western models.
In adopting the traditional idea of secular diminution of tropical year length, astronomers at the time were required only to account for the ancient records and modern data of Chinese solstitial observations by a single formula. Classical Western data, such as those listed in the Almagest of Ptolemy, became available to Asada through the Jesuit treatises. He endeavored to synthesize Western and Chinese astronomy and to give a numerical explanation, by means of a single principle, of all the observational data available to him – old and new, Eastern and Western.
Copernicus appears in the Sino‐Jesuit treatises, not as an advocate of heliocentricism but as an observational astronomer and the inventor of the eighth sphere of trepidation. He is said to have believed that the ancient tropical year was...