Joseon Dynasty’s Mobile Astrolabe Found

A portable astronomical watch known as an astrolabe, made in Joseon Dynasty in the late 18th Century, had been found and returned to Korea.

Jeon Sang-un, a science historian and member of the Cultural Properties Committee, said on Thursday that he bought and brought the astrolabe that a Japanese person took during the Japanese colonial rule after being made in 1787 back to Korea.

An astrolabe is a mobile astronomical instrument for locating the positions of stars, determining local time, and surveying longitude and latitude. While the Honjeonui, a huge celestial globe, is a fixed astronomical instrument, an astrolabe is one that can be carried. After ancient times, astrolabes were mainly produced in Arabia, and the astrolabe that was found this time was the first one made in East Asia, Jeon explained.

The astrolabe that Jeon took home was discovered in Japan in late last year and reported in academic circles. Professor Kazuhiko Miyazima at Doshisha University who investigated the relic said that the astrolabe was confirmed to have been taken by a Japanese national living in Daegu in 1930.

This astrolabe, which is made of brass and is about 17cm in diameter, is similar to those made in Arabia. Jeon added that astrolabes made in East Asia before the 19th Century have never been found up until now, so this astrolabe is the only one in East Asia.

Some words are carved on a ring on the upper part of the front side, saying that Master Yoon or his apprentice made it in 1787, and the hind upper ring says that Korea is 38 degrees north latitude.

Various circles, fan-shaped figures, names of eastern and western constellations, and the subdivisions of the seasons are carved on both its front and hind sides. Hook-shaped figures in the center of the front side indicate the direction of stars. When people adjusted a particular star on the instrument to a real star in the sky, they could find the time and the direction of other stars and the sun.

Astronomy professor Lee Yong-bok at Korea National University of Education who closely looked at the astrolabe said that he was surprised at the fact that such a correct moveable astronomical watch was made, and evaluated the astrolabe as a very important scientific cultural asset.

Jeon said that the astrolabe will be open to the public at a museum after being researched more thoroughly.