The Collaborative International Dictionary of English v.0.48:

Electro-chronograph \E*lec`tro-chron"o*graph\, n. (Astron.
   Physics)
   An instrument for obtaining an accurate record of the time at
   which any observed phenomenon occurs, or of its duration. It
   has an electro-magnetic register connected with a clock. See
   Chronograph.
   [1913 Webster]