This instrument is clear evidence of the links between the astrolabe and astrology. On one side is an astrolabe for a single latitude, and on the other an astrological volvelle, used to find the positions of planets and other celestial bodies, especially in relation to the traditional astrological houses.
This ancient Chinese map of planet Earth's northern sky is part of the Dunhuang Star Atlas, one of the most impressive documents in the history of astronomy. The oldest complete star atlas known, it dates to the years 649 to 684. In this example showing the north polar region, a very recognizable Big Dipper, part of the modern constellation Ursa Major, lies along the bottom of the chart.