Tenmon Hahakase (Doctor of Astronomy) (天文博士)

Tenmon hakase was a government post belonging to Onmyoryo (Bureau of Divination) in the ritsuryo system of ancient Japan. The status was equivalent to shoshichiinoge (Senior Seventh Rank, Lower Grade), and only one person could hold this a position at a time.

Onmyoryo consisted of three subjects--onmyodo (yin-yang philosophy), rekido (learning of the calendar) and tenmondo (ancient horoscopy)--and tenmon hakase was the teacher of tenmondo. Tenmon hakase observed the celestial bodies and reported in fortune-telling, which was sealed if there was any unusual event (it's called tenmon misso), and also taught the students the way of fortune-telling through astronomical observation.

In the middle of the Heian period, since KAMO no Yasunori taught tenmondo to ABE no Seimei, tenmon hakase also became a hereditary post of the Abe clan. The details of tenmonmisso are written in the compilation of more than 20 tenmonmisso 'Abe no Yasuchika Asonki,' as reported with the signatures of onmyojo (onmyo vice-minister) KAMO no Yasuchika and tenmon hakase, Abe no Naritoshi.