Seimei excelled in astronomy which was said to be the most difficult of all of the arts of Onmyo and he was given an important post by the 6 successive emperors; Emperor Suzaku, Emperor Murakami, Emperor Reizei, Emperor Enyu, Emperor Kazan and Emperor Ichijo as well as FUJIWARA no Michinaga and FUJIWARA no Sanesuke thereby enjoying influential power.
陰陽諸道の中で最も難しいと言われていた天文道に長じ、朱雀天皇・村上天皇・冷泉天皇・円融天皇・花山天皇・一条天皇の6代天皇、藤原道長・藤原実資に重用されて影響力をふるった。