The contribution of the solar aureole to the measurements of pyrheliometers

The fraction of the intensity measured by a currently manufactured Eppley Normal Incidence Pyrheliometer (N.I.P.), within three annular regions of the solar aureole, has been determined during eight days. This fraction was determined by measuring the adjusted voltage difference between the N.I.P. and a modified N.I.P., divided by a corrected output voltage of the N.I.P. The fraction of intensity within the aureole was generally found to have little effect on the intensity measured by the N.I.P., even on hazy days. The data taken indicates a linear relationship between the fraction of the direct beam intensity scattered into the aureole and the total extinction coefficient of the atmosphere.