Extraterrestrial solar illuminance Evo--Algorithm 1.23

The solar radiation incident on the upper atmosphere varies during the year due to the ellipticity of the earth's orbit.

Input
Extra-terrestrial illuminance at mean distance between earth & sun, klx
(A commonly-adopted value of is 127.5 klx)
Day of year, J (J=1 on Jan 1, J=365 on Dec 31)

Equation

Source
IES(1)

References
  1. IES Calculation Procedures Committee Recommended practice for the calculation of daylight availability Journal of the Illuminating Engineering Society of North America 13 (4) 381-392 (1984)
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