抄録
In many cases, the position of the sun in the sky at a certain place on the earth at a certain time in a year is calculated by using data on the latitude of the place as well as the solar declination and the apparent solar time at the time. In order to obtain the apparent solar time in Japan, it is necessary to know Japan Standard Time and the equation of time at the time, and the longitude of the place. The intensity of solar radiation on the ground is affected by the distance between the sun and the earth. Among the above-mentioned quantities, as regards the three quantities of solar declination, equation of time, and sun-earth distance, it is not easy to know their sufficiently accurate values at a certain time in a year because they change depending on the time of year. This paper presents a series of approximate equations for calculating these three quantities as functions of time passage after the vernal equinox or the perihelion.
