The quartz chronometer is the main source for keeping shipboard time
(fig. 5-5). A chronometer is like any watch except that it keeps time to a
higher degree of accuracy. For detailed information on the components
and upkeep of shipboard chronometers, refer to NSTM, chapter 252.
Error and Rate
Even a chronometer cannot keep exact time indefinitely. Sooner or later
the chronometer time gradually begins to draw away from GMT (UTC).
The difference between chronometer time and GMT, at any instant, is
called chronometer error. Error direction is identified with a sign or
letter (+ or F = Fast) or (- or S = Slow) to indicate that the chronometer is
either fast or slow in relation to the correct GMT.
Chronometer rate, on the other hand, is the amount the instrument gains
or loses in a specified time.
Figure 5-5. Quartz chronometer.