We often get asked about moonphase grandfather clocks and were they just a form of decoration or were they an important feature on antique clocks? The lunar moon repeats with a cycle of 29.5 days, this is shown on all antique clocks with a moon feature, the disc moving once or twice per day.
On early pre C.1800 examples they certainly were more of a feature that the owner required for a specific purpose. That purpose was first and foremost travel. Whether you would be travelling by ship or travelling by road, knowing when the next full moon was vital part of life back in the 18th century. A merchant might live near the coast and need to know when the next high tide was, this feature will also be accompanied by a moon disc. He could look at his clock and on that day it would say the high tide would be 7am /7pm etc.
Tidal times are sometimes stationary. i.e. set to the port of the clock, Bristol Key etc or variable by an indicator to the arch which can be set to your local port, high tide time.
On an 18th century antique clock a moon disc can either be a circular disc to the arch, a globe moon to the arch, sometimes called a ‘Halifax Moon’, or a small ‘penny moon’ normally to the dial centre, where the seconds disc normally would be. Clocks with moon discs and not accompanied with high tide indicators were for help when travelling by road. The highwayman was always a risk for the merchant in the 18th century, it was always advisable to travel on days with the full moon and lots of light. Generally the highwayman did not work on such nights, as he would be more likely to be recognised. The most famous of northern highwayman was a Edward ‘Highwayman’ Higgins, who was a gentleman by day and a thief by night. He resided on Gaskell Avenue in Knutsford, only 5 miles from where our antique clock workshop is based. Higgins was hanged for his crimes in 1767.
London longcase clocks with moon features are very collectable as London had street lighting in the 18th century and the arches on London clocks are slightly reduced and not a full semi-circle. They were not really designed for moons. On provincial clocks you will notice the arch is a full semi-circle and alot more suited to a moon disc. It is for that reason finding a genuine London 18th century clock with a moon is highly sought after. Adding this feature to an 18th century London grandfather clock, can add up to £5,000 to the price on an equivalent clock.
I have been talking above about pre C.1800 clocks and clocks where the dials are 12inches from side to side or less. Later clocks with dials of 13 inches or even larger are more likely to have moons and are not quite so rare. Clearly lots of later 19th century wider eamples can have moons. These are more common and the moon disc on these is more for a form of decoration in my opinion than for any other purpose. We stock a few good examples at http://www.pendulumofmayfair.co.uk of moon antique clocks.
Pictures of different styles of moon dials below