Constellation carved on a dolmen belonging to Ancient Korea (early 30th century B.C. - 108 B.C.) and an astronomical chart carved on a stone belonging to Koguryo Kingdom (B.C. 277 - A.D. 668) show the then development of astronomy. They prove that Koreans conducted the astronomical observation on a scientific way by making various observation means.

Among those astronomical heritages is an armillary sphere that the Korean people used in measuring astronomical data including positions of stars. It was developed by Jong Cho, Pak Yon, Jong Rin Ji and other scholars in 1433, the period of the feudal Joson dynasty.

Through the armillary sphere, the Korean people fixed the cross angle between ecliptic and equatorial planes 24 degrees, the value that almost coincides with the present astronomical data.

According to the Chronicles of the Feudal Joson Dynasty, the armillary sphere was remodeled several times.

In the 19th century, it was developed into a universal armillary sphere by Nam Pyong Chol, a famous astronomer. Nam analyzed the forte and foible of the preceding armillary spheres through books published at home and abroad and suggested a new armillary sphere, which made it possible to measure 19 kinds of astronomical data.

Meanwhile, the Korean ancestors achieved great development in introducing observed data into arithmetic processing.

Ri Sang Hyok, a gifted mathematician, in his mathematic papers published in 1855 pointed out the faults of a European scholar's computational method and described in detail the more correct and simple computational methods.

As seen above, the Korean ancestors made a contribution to developing the astronomical theory and enriching the treasure of human culture by inventing superior astronomical observation apparatuses like armillary sphere.