The apparatus used by the Rome Astronomical Observatory expedition for the measurement of the extreme solar limb darkening at the total solar eclipse, on 7 March 1970, in Mexico, is described here. For the measurements, the method of Julius is followed. The apparatus consists of a photoelectric photometer with a mechanical chopper, which alternatively inserts the different color filters. The recording and command system is also described.
G. A. De Biase, "Photoelectric System for Extreme Solar Limb Darkening Observation in Different Wavelengths with High Resolution Time," Appl. Opt. 9, 2661-2665 (1970)