Astronomy in China has a very long history, with historians indicating that the Chinese were the most persistent and accurate observers of celestial phenomena anywhere in the world before the Arabs. Star names later categorized in the twenty-eight mansions have been found on oracle bones unearthed at Anyang, dating back to the middle Shang Dynasty (Chinese Bronze Age), and the mansion (xiù:宿) system's nucleus seems to have taken shape by the time of the ruler Wu Ding (1339-1281 BC).Detailed records of astronomical observations began during the Warring States period (fourth century BC) and flourished from the Han period onward. Chinese astronomy was equatorial, centered as it was on close observation of circumpolar stars, and was based on different principles from those prevailing in traditional Western astronomy, where heliacal risings and settings of zodiac constellations formed the basic ecliptic framework.Some elements of Indian astronomy reached China with the expansion of Buddhism after the Eastern Han Dynasty (25–220 AD), but the most detailed incorporation of Indian astronomical thought occurred during the Tang Dynasty (618-907), when numerous Indian astronomers took up residence in the Chinese capital, and Chinese scholars, such as the great Tantric Buddhist monk and mathematician Yi Xing, mastered its system. Islamic astronomers collaborated closely with their Chinese colleagues during the Yuan Dynasty, and, after a period of relative decline during the Ming Dynasty, astronomy was revitalized under the stimulus of Western cosmology and technology after the Jesuits established their missions. The telescope was introduced in the seventeenth century. In 1669, the Peking observatory was completely redesigned and refitted under the direction of Ferdinand Verbiest. Today, China continues to be active in astronomy, with many observatories and its own space program.