Gaocheng Astronomical Observatory
Ancient Chinese observatory with a gnomon and Yuan-era stone structure.
The Gaocheng Astronomical Observatory, also called the Dengfeng Observatory, sits within the Duke of Zhou’s shrine in Gaocheng Town, near Dengfeng in Henan province, China. Astronomical observations were made here over a long span, beginning in the Western Zhou period and continuing into the early Yuan dynasty. The site contains a gnomon that was used for the Da Yan calendar, promulgated in 727 or 728 AD, as well as the large Yuan-dynasty observatory. In 2010, it became a UNESCO World Heritage Site as part of the “Historic Monuments of Dengfeng in the ‘Center of Heaven and Earth.’”
According to tradition, the Duke of Zhou (around 1042 BC) set up a gnomon at this location to observe the Sun, believing the area to be the center of heaven and earth. His work in mathematics and astronomy is recorded in the Zhoubi Suanjing.
During the Tang dynasty, the astronomer Yi Xing (683–727) organized a survey using twenty stations across China to measure shadow lengths and latitudes, aiming to determine the length of a meridian degree and to reform the calendar. While Gaocheng was one of the stations, it was not specifically tied to the Da Yan calendar, and the survey was not designed to measure the equation of time. The observations contributed to the creation of the Da Yan calendar, but the calendar was not uniquely associated with the gnomon at Gaocheng. There is no established evidence that Yi Xing created a physical 'Shigui chart' at the location south of the observatory in the temple dedicated to Zhou Gong.
The great observatory was built in 1276 during the early Yuan dynasty, ordered by Kublai Khan and designed by astronomers Guo Shoujing (1231–c.1315) and Wang Xun (1235–1281) to track the Sun and stars and to measure time. It was constructed from stone and brick and has two parts: the main body and the shigui (also called the ruler to measure the sky). The body alone is 9.46 meters tall, rising to 12.62 meters when the two cabinets on top are included. The gnomon is an unusual horizontal bar mounted between the two cabinets. The shigui extends 31.19 meters northward and is 0.53 meters wide, made of 36 square stones with two parallel waterways to check its level. Its alignment matches the modern method for measuring the meridian. During measurements, a beam is placed across the grooves, and a jingfu (an instrument with many holes) on the waterways measures the sh
- associated_calendars
- Da Yan calendar (727 or 728 AD), Shoushi calendar (1281)
Lore & Background
It is believed that the Duke of Zhou (c. 1042 BC) erected a Ceyingtai (observatory measuring the shade or gnomon) at this place to observe the Sun, as he believed the area to be the center of heaven and earth. His interest in mathematics and astronomy is reported in the Zhoubi Suanjing. During the Tang dynasty, astronomer Yi Xing (683–727) conducted a survey using 20 stations across China to measure shadow lengths and latitudes, aiming to determine the length of a meridian degree and to reform the calendar. Gaocheng was one of these stations, but the survey was not specifically aligned along a meridian at 114° east, and the observations were not directly tied to the Da Yan calendar in a way that overstates the gnomon's role. There is no established evidence that Yi Xing created a physical 'Shigui chart' at the location south of the observatory in the temple dedicated to Zhou Gong.
Reader's Guide
The great observatory was built in 1276 in the early Yuan dynasty on the order of Kublai Khan and designed by astronomers Guo Shoujing and Wang Xun to observe the movement of the sun and stars and to record time. Built of stones and bricks, it has two parts: the body and shigui (ruler to measure the sky). It is 9.46 meters high by itself, and 12.62 meters high including the two cabinets on top. The gnomon is a bar mounted horizontally between the cabinets, and the shigui extending north is 31.19 meters long and 0.53 meters wide, made of 36 square stones with two parallel waterways to check levelness. The very precise observations served for the new Shoushi calendar of 1281, which was in use for 364 years; the length of the tropical year was determined to 365 d 5 h 49 m 20 s, a value in accord with the Gregorian Calendar but obtained 300 years earlier. In 1787, Laplace applied these measurements to check his calculations on the secular changes of the obliquity of the ecliptic and the eccentricity of the Earth's orbit. It is the first in a series of 27 observatories built in the early Yuan dynasty.
Did You Know?
- The observatory site has a tradition of astronomical observations from the Western Zhou up to the early Yuan dynasty.
- Yi Xing built 20 standardized gnomons across China, one of which was at Gaocheng, to measure the equation of time.
- The great observatory was built in 1276 on the order of Kublai Khan and designed by Guo Shoujing and Wang Xun.
- The Shoushi calendar of 1281 determined the tropical year as 365 d 5 h 49 m 20 s, matching the Gregorian value 300 years later.
Frequently Asked Questions
What is the Gaocheng Astronomical Observatory?
It is an ancient Chinese astronomical site in Henan province that has been used for sky observations from the Western Zhou period all the way into the early Yuan dynasty. The complex includes a gnomon and a large stone observatory structure from the Yuan era.
Where exactly is the Gaocheng Astronomical Observatory located?
The site sits inside the Duke of Zhou's shrine in Gaocheng Town, near the city of Dengfeng in Henan province, China.
What makes the Gaocheng Astronomical Observatory special compared to other heritage sites?
It is one of the oldest continuously used astronomical observation sites in China, featuring a gnomon tied to the Da Yan calendar of the 8th century alongside a massive Yuan-dynasty stone structure. Its long span of active use across many dynasties at a single location is rare.
When and why did the Gaocheng Astronomical Observatory become a UNESCO World Heritage Site?
In 2010 it was inscribed as part of the grouped listing 'Historic Monuments of Dengfeng in the Center of Heaven and Earth.' UNESCO recognized it for its exceptional record of astronomical practice stretching from the Western Zhou through the early Yuan period.
Which historical calendars are linked to the Gaocheng Astronomical Observatory?
The on-site gnomon was used in the development of the Da Yan calendar, promulgated around 727 or 728 AD. The Yuan-dynasty observatory structure is also associated with the Shoushi calendar of 1281.
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