Sunset or swastamita is the time when the sun disappears below the horizon line in the west. The red color in the sky at sunset and sunrise is caused by a combination of blue Rayleigh scattering and the density of the Earth's atmosphere.
Time measurement
This diagram shows the position of the Sun after sunset, showing the effects of atmospheric refraction.
Based on astronomical calculations, the sun is said to set when the sun's visible midpoint is 50 arc minutes below the western horizon or is at 90.833° from the zenith point.[1] The resulting figure of 50 arc minutes below the western horizon is obtained from calculating the average amount of atmospheric refraction of 34 arc minutes plus the apparent radius of the sun at the western horizon of 16 arc minutes. In simple terms, the sun can be declared to have truly set when the top of the sun's visible disk is below the western horizon. Graph of variations in sunset times in the city of Palangka Raya during 2020
The exact time of sunset can vary throughout the year. These time variations are caused by the altitude, time zone, and longitude & latitude of a sunset viewing location. In addition, variations in the exact time of sunset are influenced by the tilt of the earth's axis, the daily rotation of the earth, the movement of the planets in their annual elliptical orbits about the sun, as well as the revolution of the earth and the moon around the sun. The solar analemma can also be used to determine variations in the exact time of sunset.
In the equatorial region and its surroundings, variations in the exact time of sunset are mainly influenced by the solar anema. Meanwhile, variations in the exact time of sunset at high latitudes are caused by the tilt of the earth's axis of 23.5°. In summer and autumn, the length of daylight hours gets shorter and sunset becomes earlier until the days before the winter solstice in June in the southern hemisphere and in December in the northern hemisphere. After the winter solstice until the end of spring, the length of daylight hours gets longer and the sunset time becomes longer until the days before the summer solstice in December in the southern hemisphere and in June in the southern hemisphere. northern hemisphere.
Sunset position
Based on astronomical studies, the position of the sunset tends to be in the southwest after the September equinox until the March equinox and conversely tends to set in the northwest after the March equinox until the September equinox. On the equinox, the position of the setting sun tends to be in the true west direction.
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