We have built an instrument that counts pulses from photomultipliers that look at four bands of solar continuum, recording the changes in intensity during an eclipse. We use a plywood spectrograph to select an ultraviolet band and interference filters for the others. The number of counts seen in 1/20 sec is displayed for the subsequent 1/20 sec on binary light-emitting diodes which are photographed. Our ex periment can attain a spatial resolution of better than 0.1 sec of arc and an accuracy in irradiance of better than 3%.
S. R. Weart, "Photon Counting During an Eclipse," Appl. Opt. 9, 2650-2652 (1970)