photochronograph
Pho`to*chron"o*graph, n. [Photo-+ chronograph.] 1. (Physics) 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. 2. (Astron.) An instrument for the photographic recording of star transits.