'Hangawi Full Moon' Rises on the 1st of Next Month

Full Harvest Moon on Next Month's 1st at 6:20 PM
Perfectly Round Moon Observed on 2nd at 12:20 AM

[Asia Economy Reporter Junho Hwang] The Korea Astronomy and Space Science Institute announced on the 23rd that this year's Chuseok full moon (October 1st, Thursday) will rise at 6:20 PM in Seoul.

The highest moon can be seen at 12:20 AM on the night of the 2nd, just past midnight. However, it is not the roundest moon. The moon is fully round when it is positioned opposite the sun, and the completely full moon will rise at 6:05 AM on the day after Chuseok, the 2nd. It is expected that the roundest moon can be seen near the western horizon just before the moon sets on the 2nd.

The reason the full moon is not perfectly round is that the phase of the moon rising on the full moon day varies depending on the time of the new moon (hap-sak) on the 1st day of the lunar calendar, and because the moon's orbit is elliptical, the time it takes to go from the sun's direction to the opposite side is not constant.

The 1st day of the lunar calendar includes the time when the moon passes in the same direction as the sun (new moon), and lunar dates are assigned at equal intervals (24 hours) from that day. For example, if the new moon occurs late at night on the 1st day of the lunar calendar, the moon rising on the 15th day may not be fully round because it has not yet reached the opposite side of the sun.

Due to the elliptical orbit of the moon, the actual time it takes to face the opposite side of the sun (full moon) is also not constant, so the perfectly full moon may occur before or after the 15th day of the lunar calendar. These two main reasons can cause the full moon to not be perfectly round. The new moon time for the 8th lunar month this year is 8 PM on September 17th (solar calendar).

The moonrise times for each region can be checked on the Astronomy Institute's website.