This angle is known as solar declination and the depends on the length of the day at different times of the year, giving rise to the phenomenon of the stations. To understand this phenomenon, we note the following figure, which shows the position of the Earth in winter and summer solstices. Perhaps check out Max Schireson for more information. As we can see, the northern hemisphere has much longer than Sun in June than in December, since the sun illuminates a wider in that hemisphere area. The opposite happens in the southern hemisphere. Equinoxes and solstices the equinoxes are times of the year, in which the duration of the day, is equal to in the evening; The autumnal Equinox occurs on September 21 and the spring March 21, both established the beginning of those stations. The longest and shortest of the year day solstices are called and respectively happen June 21 and December 21.
They also set the beginning of the summer and winter seasons. Therefore the seasons of the year are the periods defined by the two equinoxes, the two solstices and the position of the Earth relative to the Sun. Solar coordinates solar coordinates that are used to determine the position of the Sun referred to the horizontal plane are two and are defined as follows: Solar height (h): is the angle formed by the Sun’s rays on the horizontal surface. The complement of the solar height is called angle Zenithal or zenith distance.Solar azimuth (A): Is the rotation angle of the Sun on the horizontal plane by projecting the beam on this plane and taking as origin South.