Enter the photoelectric cell

Stebbins was not completely satisfied with the selenium photometer.  The cells were not very sensitive, only stars brighter than the third magnitude could be studied.  They also had a narrow spectral response, were not readily available, were difficult to work with and the characteristics varied from one cell to another.  The solution to Stebbins' problems was found in physicist Jakob Kunz.  Kunz was born and educated in Switzerland and, after advanced studies in England, emigrated to the United States.  Kunz was an excellent theoretical physicist who enjoyed experimentation and felt the best things in physics were in the sky.

 Kunz had worked with and manufactured photoelectric cells since 1909.  A photoelectric cell produces a current when light falls on the metal surface and ejects an electron.  In the autumn of 1911, Kunz met Stebbins and suggested he try a photometer based on photo emissive cells instead of selenium.