Photochronograph /(?)/

Pho·to·chron·o·graph

Photochronograph

n.
  1. 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. (Physics)
  2. An instrument for the photographic recording of star transits. (Astron.)