How to set the moon dial on
your clock
Some clocks have a dial to
show the phases and age of the moon. There are
several types of moon dial, the commonest being
what is called a 'rolling' moon, which is a
disc set on the very top of a clock dial, called
the arch. The moon dial is designed to show
the shape of the moon as it appears in the sky,
the number alongside it being the lunar date.
This is not the same thing at all as the calendar
date. A lunar month has consistently twenty
nine and a half days in every month and these
are usually lettered in Arabic (English) numerals.
Some moon dials also incorporate a tidal dial
showing high water times at a certain port,
sometimes several ports at once. Tide times
are normally lettered in Roman numerals.
The current lunar date can
be established by reference to a calendar or
diary - many show a white circle to mean a full
moon and a black circle to mean a new moon (i.e.
no moon). Look up the last nearest full or new
moon setting and add the number of days since
then to ascertain today's correct lunar date.
Once set, the moon dial stays accurate for the
year, and does not need constant re-setting
as a calendar dial does.
The disc of a rolling moon
turns clockwise; most will not allow turning
anti-clockwise. It will probably be 'in drive'
(i.e. changing) during a period of about three
hours in every twelve, and cannot be re-set
when in drive. At other times the moon disc
will be free to turn clockwise until the appropriate
lunar date is showing. Most moon dials have
a ratchet to prevent the dial slipping back
again. This will be visible behind the dial,
usually at the top. If re-setting the moon dial,
be careful not to inadvertently disengage the
ratchet.
If the moon does not progress
as the clock runs, then the moon drive mechanism
is probably faulty or lacking, and needs the
attention of a restorer.
Copyright
© 2001 Brian Loomes
|
