The Beijing Ancient Observatory

My wife, Hang, and I made a trip to Beijing, China, in late May - early June of 1998 to visit her family and to present workshops at Capital Normal University, her alma mater. One of the places we visited during our stay was an ancient observatory located in the southeast part of the city. Built in 1442 during the Ming Dynasty, the observatory was home to several large bronze instruments for measuring the positions of the sun, moon, planets, and stars. Even though the observatory was in use after the invention of the telescope, all observing was naked eye--there are no telescopes installed. It turns out that most of the instruments presently installed are fairly "modern", having been built in the 17th and 18th centuries. One device on display is a replica of a 15th century instrument that had been moved to an observatory in Nanjing in the 1930s.

Here is a list of the names of the instruments and what they were used for.

• Armillary Sphere
  Used to measure the coordinates of celestial bodies. There were two types, an ecliptic armillary used to track the sun, and an equatorial armillary for other bodies.

• Quadrant
  Used to measure alitudes or zenith locations of celestial bodies.

• Theodolite
  Used to measure altitude and azimuth coordinates of celestial bodies.

• Azimuth Theodolite
  Used to measure the azimuth coordinate of celestial bodies.

• Sextant
  Used to measure the angular distance between celestial bodies and to measure the angular diameter of the sun and moon.

• Celestial Globe
  Used to determine the rising and setting times of celestial bodies as well as determining the altitude and azimuth of celestial bodies at any time.

We took pictures, but many instruments were hard to photograph because they are presently surrounded by fences. The weather was also very hot and hazy, and the bright sky interfered with photography. We bought a collection of postcards which show nicer images, and I have included some of those pictures along with our own.

Click on the thumbnail image for a larger picture.

This photo of the observatory itself was copied from a postcard. As the city has grown, the observatory has been surrounded by highways, and one no longer has such a pleasant view of it.

This is a view of the observatory the second of several times we drove by it. It took a few tries before we figured out how to reach it from the two limited access roads that pass it on two sides.

We finally made it to the observatory. This photo shows me with Prof. Zhang Cumlin, the assistant chairman of the Physics Department at Capital Normal University, at the entrance to the observatory's courtyard. The top two characters in the sign mean "Beijing", the third character is "Ancient", and the bottom three characters are "Observatory".

There is a museum on the observatory grounds housing an exhibit on Chinese astronomy. This photo shows a wooden astronomical clock with an armillary sphere at its top.

This is a replica of a simplified armillary that was built in 1439, during the Ming Dynasty. The original was moved to the Purple Mountain Observatory in Nanjing in the 1930s.

This is a picture of the actual armillary taken from a postcard. It shows the instrument from the opposite side.

This equatorial armillary was built in 1673, during the Qing Dynasty. I'm in the picture to provide a sense of scale for the large size of all the instruments. There is also a 1673 ecliptic armillary.

This ecliptic armillary was built in 1744, during the Qing Dynasty. My wife Hang and Prof. Zhang are standing in front of it to provide a sense of scale. Note that the ecliptic armillary is a little more complex than the equatorial armillary.

This shows the observatory's theodolite, which was built in 1715 (Qing Dynasty).

The azimuth theodolite, built in 1673 (Qing Dynasty). I like the dragons, which are a common motif in Chinese art. (There was a large satellite dish and a construction crane visible behind the theodolite. They distracted from the image, so I removed them during processing.)

The quadrant, built in 1673 (Qing Dynasty). Notice the dragon...

The sextant, which was built in 1715 (Qing Dynasty). Notice the large gear, which is turned by a much smaller gear on a handwheel. This allows for precise adjustment of the sextant's position.

This shows the celestial globe, which was made in 1673 (Qing Dynasty). By using the wheel attached to the polar axis, the globe can be turned to show the positions of the stars at any time of the day. Note that the polar axis has apparently been moved away from the correct setting for Beijing, which is about 40^o.

This picture of the celestial globe was copied from the brochure given to visitors as they enter the observatory. Usually, people are kept away from the instruments by fences, but a couple of people were allowed in for the photo. The polar axis also appears to be set correctly in this picture.

The celestial globe was one of my favorite things in the observatory, so here's yet another picture of it from a postcard. The stars are easily visible in this photo, and the polar axis seems to be set correctly. (The postcard picture had some defects, which I removed during processing.)

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