Link to Moon phase clocks for sale

Moon Dials

Humankind has long been fascinated by the moon, before the days of widespread education a large arcane object traversing the night sky, shining brightly and mysteriously changing shape in a regular sequence.

The early clockmakers were aware that a lunar month is very close to 29½ days duration and that this could be shown on a clock dial with a wheel of 59 teeth pushed around twice daily from the hour wheel. Moons then developed through the history of longcase clocks.

Moon-phase longcase clocks were more luxurious variants so their cases would normally reflect this by being the more up-market types available for the period. A nice moon-dial movement in a basic looking case may arouse suspicion that it is not original.

Moon dial examples seem to make up roughly about 10% of all antique longcase clocks. Not especially rare considering the numbers made but generally more desirable in the clock market today. London moon dials clocks are less common, this is attributed to the early provision of street lighting in London compared to other towns/ cities.

Penny moons

These are the earliest form of moon-phase indication in longcase clocks, although they do persist for most of the 18^th century in some form. Initially a small (penny sized) aperture was made in a square dial, a disk with engraved moon face was mounted behind the dial and rotated from the hour hand pipe. The moon face was silvered, the rest of the disk darkened to represent the night sky. There would also be a calibration on the disk from 1 to 29 ½ which showed in a separate aperture or an extension of the main one. Sometimes an additional pierced plate was used behind the dial to more closely represent the shape of the waxing and waning moon.

With the advent of arched dial clocks (around 1720) penny moons often moved to the arch, the typical format was to have a separate calibrated chapter ring with a hand attached to the moon disk to show and adjust the position. The moon disk was now further from the hour wheel so additional mechanism was required, sometimes extra wheelwork (idlers) to transfer the drive, sometimes sprung levers to push the moon disk around.

Some square dial clocks were made throughout the 18^th century and into the painted dial era. The early penny moon evolved into larger, often painted moon faces. Also ‘axe-moons’ (an axe shaped segment of the moon was visible) and ‘Halifax moons’, almost always situated below the 12 o’clock number.

Full arch moons

These fairly quickly followed penny moons from the 1720s onwards. The majority of the arch became an aperture to show a moon disk which now had two separate moon faces. This was because half of the moon disk was always behind the dial. The moon appears to rise and fall between two hemispheres which are part of the main dial. Calibration for the lunar day was initially on the outer part of the moon disk, then later 1700s moved to be on the main part of the dial. Normally the moon disks now had double the number of teeth (118) and were still driven from the hour wheel in some form, either by an extra idler wheel or some form of lever reset by gravity or a spring mechanism.

The styles of moon disks show a fairly logical progression through the 18^th century. The earliest had silvered moon faces and silvered stars in between. The next type is to have silvered faces with gilt painted stars instead. Then painted moon faces and stars, finally painted moon faces and painted scenes in between often of ships and country scenes/ buildings. This final style persisted until the ‘end’ of longcase evolution around 1870. While the different styles can be used as means to date clocks, it is a little unreliable due to some clockmakers persisting with what would be considered ‘older’ styles, for example I have seen silvered moons on clocks from the later 18^th century which appear to be original.

The arch moons became an important focal aspect (any portrayal of a face naturally draws the eye) and the different styles are fascinating. Silvered moons tend to give an older look and can vary in the depiction of facial features, some very simple, others with lots of engraved ‘shading’ to create the impression of depth. Painted moons can vary from early, slightly grotesque or impish faces to very human, almost ‘judge-like’ features, looking down on the humans living out their lives below. The early period of painted dials by James Wilson (1770s to 1809) almost invariably had beautifully painted and very detailed moon faces, these are among my favourites. Later painted moons from 1820s onwards are variable in quality, some are ok but many lack detail and can frankly look a bit ugly.

Some of the better clockmakers slightly modified the moon drive mechanism by combining it with the date drive. This is more common in the large Liverpool/ Manchester clocks with ‘centre’ calendars from 1750s onward but occasionally others as well. The traditional calendar drive would have a ’24 hour’ wheel so this could drive the moon disk as well if positioned correctly. To do this the seconds arbour commonly had a bridge, the pipe of which formed the support for the date/ moon drive wheel. Occasionally the amount of teeth on the moon disk are reduced to 59, or alternatively the drive wheel can have two separate pins or flags to drive the moon disk every 12 hours.

Spherical moons and other rare types

Spherical, or ‘globular’ moons take the process of representing the changing moon a bit further. A globe moon sits in a recess in the arch and rotates to show the current moon-phase. The calibration is then shown on a silvered chapter ring by a small pointer. These are very rare movements.

Another rare type I have seen is an inset painted scene with moon and a movable ‘dark’ moon face which moves over the bright painted moon to indicate how much is showing. The calibration goes from 15 (full moon) to the next 15 at which point it springs back to the start again. This appears to have been used by a handful of makers around the 1770s in the North-West of England.