Appointment and Dismissal of Gwansanggam Jejo and Their Activities during the Reign of King Jeongjo

Gwansanggam Jejo (觀象監提調) were in charge of Gwansanggam (The office for Observation of Natural Phenomenon) along with Yeongsa (領事). King Jeongjo appointed Gwansanggam Jejo in the hodae (互對) manner during the first half of his rule, but in the second half, he appointed them in the sanghwan (相換) method of changing the positions of ministers or in the teukji (特旨) method of appointment, specifically considering their expertise. At this time, Jejo were appointed when more than half were senior rank two (正二品) officials, and more than 90% were from Hanseong (漢城) and its suburbs, and were from the former Yeongsa and Jejo families. In the field of astronomy, Gwansanggam Jejo led the publication of various calendars, such as Cheonseryeok (千歲歷) and Imja year (壬子年, 1792) Supplementary Calendar, which also increased the supply of calendars. Gwansanggam Jejo Seo Ho-su (徐浩修) selected Kim Yeong (金泳), and instructed him to build astronomical instruments to calculate the accurate time, to write related books, and publish Gukjoyeoksanggo (國朝曆象考). In the fields of Geumlu (禁漏) and Myeonggwahak (命課學), talented Gwansanggam Jejo also participated in systematizing the two organizations. In particular, they placed Myeonggwahak on the level of an astronomical organization. In addition, some Gwansanggam Jejo displayed excellent ability in Gwansanggam's regulatory enactment and financial management.