Korea had long since observed and recorded astronomical phenomena.
In the period of the Three Kingdoms (early 3rd century B.C.-A.D. mid-7th century during which Koguryo, Paekje and Silla, the feudal states in Korea, existed), astronomers made a detailed observation and records of not only the solar and lunar eclipses which occurred periodically but also the date, time, position, direction, size and colour of comets.
A historical book Samguksagi (Chronicles of the Three Kingdoms) compiled in 1145 recorded in the main part of Koguryo (277 B.C.-A.D. 668) the observation of a comet in November 46. It is the oldest among the records of comet in Korea.
The polar lights, a phenomenon rare to be seen in Korea, were observed on June 9, 1519. The record read as follows:
A strange astronomical phenomenon was observed. There was a very bright moonlight and a thin cloud cover in the west early in the evening before a light was witnessed through the clouds. It looked like a lightning but a light.
There was also a record of observation of the sun.
Sunspots were observed in the period of Koguryo. A record said that the sun’s rays disappeared and appeared again three days later.
The word “the sun’s rays disappeared” implied that one could easily see spots or many black patches on the surface of the sun if one observed it carefully when it was in yellowish brown colour at sunrise or sunset. This meant that sunspots were witnessed for three days before disappearing.
Sunspots were observed in a more specific way in the period of Koryo (918-1392).
Recorded in the astronomical part of a historical book History of Koryo Dynasty compiled in 1451 are more than 50 records about the observation of sunspots from January 1105 to the closing years of Koryo.