Takahashi Yoshitoki

Takahashi Yoshitoki (高橋至時, December 22, 1764 – February 15, 1804) was an astronomer in mid-Edo period Japan, noted for his work in calendar reform, and as the teacher of the surveyor Inō Tadataka.

Inō was interested in the problem of determining the true length of a Meridian arc, and walked the distance from his home in Fukagawa to Takahashi's observatory in Asakusa to obtain the data necessary for a rough calculation.

In 1796, Takahashi received official approval for his new calendar, and was ordered make astronomical observations between Edo and Kyoto, where he had to convince the influential Tsuchimikado clan, a clan of court nobility who advised the Emperor of Japan on ceremonies tied to the calendar dates, on the validity of his reforms.

On the other hand, he was aware that the calendar still had a few shortcomings and between staying up all night for astronomical observations and travels to Kyoto to speak with the Tsuchimikado clan, his health deteriorated and he developed tuberculosis.

Working day and night, his research on the book in the six months between late 1803 and early 1804 formed a manuscript over 2000 pages long, and caused a series relapse in his illness.