The Altazimuth was made in the eighth to twelfth year of the reign of Emperor Kangxi (1669-1673), under the supervision of the Belgian missionary Ferdinand Verbiest. It was the only one of the six instruments designed by Ferdinand Verbiest, which could not find a model from the instruments of Tycho. This instrument weighs 1811 kilograms and is 3.201 meters high, located on the top platform of Beijing Ancient Observatory. It is mainly used to measure the longitude and azimuth of celestial bodies.