Yoshimasa was recommended by KAMO no Yasunori to be a student of Astrology (the studenthood belonging to the office of Ommyo to learn astrology from the astrologist) in 970 ("Ruiju fusensho"; A collection of official documents dating from the years 737 to 1093).
吉昌は天禄元年（970年）に賀茂保憲の推挙で天文道の学生である天文得業生に補された（『類聚符宣抄』。