A dataset containing wavelengths at a 5 nm interval (300 nm to
830 nm) and the corresponding spectral energy irradiance normalized to 1 at
560 nm. Spectrum approximates the midday solar spectrum at middle latitude
as 'corresponds' to the white point of a black body a 6504 K. Original data
from http://files.cie.co.at/204.xls downloaded on 2014-07-25 The
variables are as follows: