This article examines how the political status of Gwansanggam (觀象監) astronomers changed by focusing on An Gukbin (安國賓), an astronomer who worked in Gwansanggam the mid- and late-eighteenth century. An Gukbin was the first Gwansanggam bureaucrat to rise to the first rank, or jong-1 office of Sungjeongdaebu (崇政大夫). King Yeongjo regarded An as an astronomical expert and consulted with him on astronomical issues. This article tracks what An Gukbin did to rise to such a political position, examining what astronomical tasks An actually carried out in the mid- and late-eighteenth century, how his astronomical expertise was used in the royal court of the Joseon Dynasty, and how he was treated.