  A stroboscope designed to observe pulsars in the optical spectrum is
presented. The absolute phase of the stroboscope is synchronized to better than
2.5 microseconds with the known radio ephemerides for a given pulsar. The
absolute timing is provided by the GPS clock. With such a device phase resolved
photometry of pulsars can be performed. We demonstrate the instrument's
capabilities with the results of a set of observations of the Crab pulsar, the
brightest of the known optical pulsars, with a visual magnitude of 16.5, and a
rotational frequency of ~29Hz.
