Dengfeng Observatory, Dengfeng, Henan 河南登封观星台
The Dengfeng Observatory stands at Gaocheng in Dengfeng. It was one of the stations that the Yuan astronomer Guo Shoujing set up around the country to compile the Shoushi calendar, and is the oldest surviving observatory in China. The tower is a tall square platform of brick and stone with a vertical groove up the middle of its north face, where a gnomon once stood; a long stone scale (gui) laid on the ground to the north recorded the length of its shadow, from which the solar terms were fixed. Gaocheng is traditionally held to be where the Duke of Zhou measured shadows, and a Tang-dynasty stone gnomon was erected here. The observatory is a component of the World Heritage Site “Historic Monuments of Dengfeng in “The Centre of Heaven and Earth””.
