The contribution of the solar aureole to the measurements of pyrheliometers

The fraction of the intensity measured by a currently manufactured normal incidence pyrheliometer (NIP) within three angular regions of the solar aureole has been determined during eight days. This fraction was determined by measuring the adjusted voltage difference between the NIP and a modified NIP, divided by a corrected output voltage of the NIP. The fraction of intensity within the aureole was generally found to have little effect on the intensity measured by the NIP, even on hazy days. The data taken indicate a linear relationship between the fraction of the direct beam intensity scattered into the aureole and the total extinction coefficient of the atmosphere.