After the advent of the galvanic telegraph, it became possible to electrically trigger a gun remotely, and since 1864 the Noon Gun has been fired directly from the master clock of the oldest timekeeper in the country, the South African Astronomical Observatory.
A South African Navy duty officer is present to manually fire the backup gun in case of some failure with the active gun.
According to local tradition, the initial purpose of the gun was to allow ships in port to check the accuracy of their marine chronometers (a precision instrument used aboard ships to help calculate longitude).
The gun report might be too inaccurate for ships several kilometers away if they did not correctly compensate for the relatively slow speed of sound.
For this reason ships marked their time by the puff of smoke rather than the sound, and this is one reason the guns are sited high above Cape Town Harbour.