Solar azimuth angle
Encyclopedia
The solar azimuth angle is the azimuth angle of the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

. It is most often defined as the angle from due north in a clockwise direction.



It can be calculated in various way. In different times, it has been explained in different ways. It can be calculated, to a good approximation, using the following formula, however angles should be interpreted with care due to the inverse sine, i.e. x = sin−1(y) has more than one solution, only one of which will be correct.



The following two formulas can also be used to approximate the solar azimuth angle, however because these formulas utilize cosine, the azimuth angle will always be positive, and therefore, should be interpreted as the angle less than 180 degrees when the hour angle, h, is negative (morning) and the angle greater than 180 degrees when the hour angle, h, is positive (afternoon).





The previous formulas use the following terminology:
  • is the solar azimuth angle
  • is the solar elevation angle
    Solar elevation angle
    The solar elevation angle is the elevation angle of the sun. That is, the angle between the directionof the geometric center of the sun's apparent disk and the horizon...

  • is the hour angle
    Hour angle
    In astronomy and celestial navigation, the hour angle is one of the coordinates used in the equatorial coordinate system to give the position of a point on the celestial sphere....

     of the present time
  • is the current sun declination
  • is the local latitude
    Latitude
    In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...


Solar elevation angle

Sun height, height angle, solar altitude angle or elevation (gS) is the angle between a line that points from the site towards the centre of the sun, and the horizon. The zenith
Zenith
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e...

 angle is the opposite angle to the sun height (90° – gS). At a sun height of 90°, the sun is at the zenith and the zenith angle is therefore zero.

See also

  • Horizontal coordinate system
    Horizontal coordinate system
    The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane. This coordinate system divides the sky into the upper hemisphere where objects are visible, and the lower hemisphere where objects cannot be seen since the earth is in...

  • Azimuth
  • Sun
    Sun
    The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

  • Sun path
    Sun path
    Sun path refers to the apparent significant seasonal-and-hourly positional changes of the sun as the Earth rotates, and orbits around the sun. The relative position of the sun is a major factor in the heat gain of buildings and in the performance of solar energy systems...

  • Sunrise
    Sunrise
    Sunrise is the instant at which the upper edge of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the point at which the sky begins to lighten, some time before the sun itself appears, ending twilight...

  • Sunset
    Sunset
    Sunset or sundown is the daily disappearance of the Sun below the horizon in the west as a result of Earth's rotation.The time of sunset is defined in astronomy as the moment the trailing edge of the Sun's disk disappears below the horizon in the west...

  • Solar tracker
    Solar tracker
    A solar tracker is a generic term used to describe devices that orient various payloads toward the sun. Payloads can be photovoltaic panels, reflectors, lenses or other optical devices....


External links

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