We investigate the astronomical phenomenon records of Sukjong’s 𝐶ℎ𝑢𝑛𝑏𝑎𝑛𝑔-𝐼𝑙𝑔𝑖 made by 𝑆𝑖𝑔𝑎𝑛𝑔𝑤𝑜𝑛 (Royal Educational Office of the Crown Prince) at which King Sukjong was the crown prince (i.e., 1667 January 24–1674 September 22). From the daily records of 2,799 days, we extract the astronomical records of 1,443 days and classify them into 14 categories. Then, we group the records of each category into five phenomena (Atmosphere, Eclipse, Daylight Appearance, Apparition, and Appulse) and compare them with the results of modern astronomical computations wherever possible. Except for Atmosphere group comprising records of meteorological events, such as solar halo, lunar halo, and unusual clouds, the significant findings in every other group are as follows: In Eclipse group, the solar eclipse that occurred on 1673 August 12 was unobservable in Korea, which is in contrast to the record of 𝐽𝑜𝑠𝑒𝑜𝑛𝑤𝑎𝑛𝑔 𝑗𝑜-𝑆𝑖𝑙𝑙𝑜𝑘 (Annals of the Joseon Dynasty), which states that the sun was in eclipse around sunset time, as observed at 𝑁𝑎𝑚 mountain. From the lunar eclipse records, we verify that the Joseon court did not change the date of the events observed after midnight. In Daylight Appearance group, we confirm that this phenomenon was observed during the daytime and not during twilight. We further suggest that if observation conditions are met, a celestial body brighter than −2.3 mag could be seen during the daytime with the naked-eye. In Apparition group, we find the possibilities that the Orionid meteor shower had influence on the meteor records and the seasonality on the aurora records. We also find that the Korean records in which the coma of comet C/1668 E1 was located below the horizon were overlooked in previous studies. Finally, we find that the records of Appulse group generally agree with the results of modern calculations. The records of 𝐵𝑒𝑜𝑚 (trespass in literal) and 𝑆𝑖𝑘 (eating in literal) events show average angular separations of 1.2◦ and 1.0◦, respectively. In conclusion, we believe this work helps study the astronomical records of other logs of 𝑆𝑖𝑔𝑎𝑛𝑔𝑤𝑜𝑛, such as Sunjong’s 𝐶ℎ𝑢𝑛𝑏𝑎𝑛𝑔-𝐼𝑙𝑔𝑖.

We investigated the records of astronomical phenomena in the Hyeonjong-Donggung-Ilgi written by the educational office for a crown prince, Sigang-won, during the time of a crown prince of the king Hyeonjong (i.e., from 1649 to 1659). Of the total of 3,625 days, 3,044 astronomical accounts were compiled from astronomical records of 2,003 days. We classified these astronomical accounts into 16 items, grouped into five categories, and statistically analyzed each group. In our analysis, the accounts for atmospheric optical phenomena equates to 57.9% of the total, and for celestial phenomena visible during the daytime the percentage is 17.3%. The records related to the approach between two objects such as planets, moon, and stars account for 3.3%, and solar or lunar eclipses take up 0.6%. The ratio of accounts regarding meteor, comet, and fire light (火光) stand at 13.8%, 0.30%, and 6.8%, respectively. Sunny days account for 71.1% of all days per year during this period. We determined that the distribution of the fire light by month is similar to that of the solar halo. We also found that the astronomical records from the Annals of the Joseon Dynasty correspond to only 30% of those of the Hyeonjong-Donggung-Ilgi for the same period. In particular, the phenomena of celestial objects occurring outside the atmosphere are transmitted to the Annals of the Joseon Dynasty in a higher proportion than the phenomena inside the air. It is therefore necessary to use a historical diary like a Donggung-Ilgi to interpret the phenomena in the air such as atmospheric optical events, meteor, and fire light.

We study the correlation between distributions of astronomical records and historical events using historical meteor (shower) records. In Korean chronicles, planets and meteor (shower) records are the most abundant astronomical phenomena. And they represent a general tendency of the number distribution of whole astronomical observations. We examine the correlation for the number distribution between meteors (showers) and planets during A.D. 1200-1700 and find that both records have a similar distribution. We classify historical events into three grades according to the social impact, and investigate the correlation between distributions of meteor (shower) records with social events, such as, new king's accession to the throne, foreign invasions, and domestic turmoils. From the statistical analysis, we cannot find any correlation between the meteor (shower) records and the political events. Therefore, we conclude that Korean historical records have not been influenced by the political events. We also examine the correlation between Chinese and Japanese meteor (shower) records and political events for A.D. 1200-1700, respectively, but cannot find any correlations between them.

We have constructed a database of Korean historical astronomical records. The database contains observational data recorded from BC 2183 to AD 1910. We have also built a webpage for searching through the database based on the following criteria: (1) dynasties (2) astronomical phenomena (3) reigning kings (4) references (5) keywords. Users may select two or more dynasties to search through the database for a certain phenomena, and compare data with those of other dynasties. The queried data can be primarily sorted by one critetion, and secondarily sorted by another, each in ascending or descending order. The search results give dates both in Solar and Lunisolar calendars, years and dates in Sexagenary cycle, dynasties, reigning kings, astronomical phenomena, and references. The database and webpage were constructed under the research project of the Korean Astronomical Data Center (KADC, http://kadc.kao.re.kr) in Korea Astronomy Observatory (KAO).

Events of eclipses as well as other major astronomical events observable in the eastern sector of Asian continent are computed and checked with astronomical records of antiquity. Particular attention was given to two types of the events recorded in remaining records of Dangun Chosun Period (DCP): (1) concentration of major planets near the constellation of Nu-Sung ( β A r i e s ) and (2) a large ebb-tide. We find them most likely to have occurred in real time. i.e., when the positions of the sun, moon, and planets happen to be aligned in the most appropriate position. For solar eclipses data, however, we find among 10 solar eclipse events recorded, only 6 of them are correct up to months, implying its statistical significance is no less insignificant. We therefore conclude that the remaining history books of DCP indeed contains important astronomical records, thereby the real antiquity of the records of DCP cannot be disproved.

Astronomical records in the days of King Jeongjo of Yi dynasty, 1777-1800, are examined for solar and lunar eclipses, meteors and comets. The books used for this investigation are Sung Jeong Won Il Gi, which are the original daily records written in the court. The records found in these Sung Jeong Won Il Gi are tabulated according to the four astronomical phenomena above, and they were cross checked with the records in the book, Jung Bo Mun Heon Bi Go. Although Jung Bo Mun Heon Bi Go has most frequently been used as the original records to those who work for the ancient Korean records, the inaccuracy and the deficiency are found.