Huangjing

Huangjing

The Yellow meridian refers to the longitude in the celestial Zodiac coordinate system. It is a coordinate value used to determine the position of celestial bodies on the celestial sphere in the ecliptic coordinate system, measured eastward from the vernal equinox. In this system, the celestial sphere is divided into North and south hemispheres by the celestial equatorial plane.

The ancient people called the sun's annual apparent motion line (that is, the reflection of the earth's orbit on the celestial sphere) the ecliptic, and the Yellow meridian is the metric coordinate (longitude) on the ecliptic. The current 24 solar terms are divided into 24 equal parts according to the degree of the Yellow meridian, and each equal part is 15 degrees.

Astronomical significance

The Yellow meridian refers to the longitude in the celestial Zodiac coordinate system. The ecliptic refers to the path of the sun across the celestial sphere in a year. It crosses the celestial equator twice a year, one at the vernal equinox and the other at the autumnal equinox. Since there is no obvious point on the ecliptic that can be used as longitude 0 of the ecliptic, the vernal equinox is arbitrarily designated as the position of longitude 0 of the ecliptic. The longitude of the celestial body is the angular distance from the celestial body to the vernal equinox. ecliptic coordinates are very useful for celestial bodies in the solar system. For example, the longitude of the sun given in the almanac is measured by the Yellow longitude. The earth revolves around the sun for about 365 days, 5 hours, and 940 million kilometers. This orbit is called "the Yellow meridian of the sun".

Degree division

According to astronomical practice, the vernal equinox is taken as the starting point and measured from west to east at 360 degrees. The 24 solar terms used since 1645 are divided according to the degree of the solar meridian. The 360 degree circle of the ecliptic is divided into 24 equal parts, each equal part is 15 degrees, and every 15 degrees is a solar term. There are 24 solar terms in the whole year. The degrees of the solar yellow meridians of the 24 solar terms are: Spring: 315 degrees at the beginning of spring, 330 degrees in rain, 345 Degrees in stung, 360 degrees in equinox, 15 degrees in Qingming and 30 degrees in Guyu. summer: 45 degrees in early summer, 60 degrees in Xiaoman, 75 degrees in mangzhong, 90 degrees in summer solstice, 105 degrees in Xiaoshu, 120 degrees in Dashu autumn: 135 degrees in early autumn, 150 degrees in Chushu, 165 degrees in Bailu, 180 degrees in autumnal equinox, 195 degrees in Hanlu, 210 degrees in frost winter: 225 degrees in early winter, 240 degrees in Xiaoxue, 255 degrees in dashue, 270 degrees in winter solstice, 285 degrees in Xiaohan, 300 degrees in Dahai.

Chinese PinYin : Huang Jing