Constructor - Eugen Hammermüller
Manufacturer: Eugen Hammermüller
Serial number: No.2
Year of production: unknown
The production date or the date when this instrument was purchased is not known, but it is known that from March, 1892 Mohorovièiĉ used it to determine the time of the passage of the stars through the local meridian, in order to determine the absolute time and correction of the observatory clocks – most probably Arway chronometer and König pendulum clock. Later, along with this procedure he measured air pressure and temperature in order to determine empirical correlation between those values and the clock drift.
The passage instrument has not been used since the year 1913. Since then a crystal radio-detector was used for determining the drift of the observatory clocks by receiving the coincidence time-signal from Paris.