Comparison between calculated uncertainties and the standard deviation of real solar measurements: the CSU (%) for a SSI measurement with infinite integration time (blue); the calculated CSU for a SSI uncalibrated measurement with an integration time of 0.6 s and no uncertainty contribution from the response curve (green); and the measured standard deviation of the uncalibrated SOLAR/SOLSPEC as observed from a single solar measurement using a 0.6 s integration time (red).