Sacheondae and Seoungwan — Astronomy in Goryeo

Also called: Seoungwan, Sacheondae

Goryeo set up the Sacheondae as its astronomical office and later merged it with the Taesaguk into the Seoungwan.

Linking changes in the heavens to affairs of state, Goryeo valued astronomical observation. The early Taebokgam was renamed Sacheondae in 1023 (Hyeonjong 14), and after further renamings (Sacheongam and others) it was merged in 1308 with the Taesaguk, in charge of the calendar, to form the Seoungwan. The Seoungwan handled astronomy, the calendar, weather observation and timekeeping, and passed to Joseon (renamed Gwansanggam under Sejo). The astronomy treatise of the Goryeosa preserves many records of eclipses, comets and sunspots, and west of Manwoldae in Kaesong stands a Cheomseongdae said to be Goryeo’s observatory.

For the calendar Goryeo first used Tang’s Xuanming calendar, then adopted Yuan’s Shoushi calendar under King Chungseon.