Photochronograph

·add. ·noun An instrument for the photographic recording of star transits.

II. Photochronograph ·add. ·noun An instrument for recording minute intervals of time. The record is made by the power of a magnetic field, due to an electric signaling current, to turn the plane of polarization of light. A flash, coinciding in time and duration with the signal, is thus produced and is photographed on a moving plate.