It began with a selenium cell

Joel Stebbins, arrived at Illinois in 1903 fresh from completing his PhD at Lick Observatory. An avid observational astronomer, he began an observing program using the Pickering visual program surveying stars in search of undetected eclipsing binary stars. Later in 1904, he began the estimates of the relative magnitudes of 107 double stars, duplicating the work of astronomer E.C. Pickering in 1878.  This project leads to a revolution in astronomical photometry.