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Setting the Moon Dial on Your Grandfather Clock

Posted by Gregory Burton on


Many grandfather clocks incorporate a moon dial. This sophisticated piece of technology is designed to show the shape of the moon as it appears in the sky, as well as the lunar date. Depending on how basic or advanced your moon dial is, it may be more or less detailed or advanced. However, setting the moving dial is a relatively simple procedure that can be performed with minimal hassle.


Apply Pressure and Rotate Accordingly

To begin, place your fingers on the front of the clock’s moon dial and apply slight pressure. Then, carefully rotate the moon dial clockwise until the moon is situated directly parallel to the number 15 on the dial’s face. If the moon dial will not rotate, wait 6 hours before trying again. It is crucial that you never force the dial to move if it cannot do so with relative ease, as it may be in the midst of a cycle.


Determine the Accurate Date

By consulting an almanac, calendar, or modern chart, learn the exact date of the last full moon, and count the number of days that have passed since then. Next, turn the moon dial clockwise one click for each day that has passed since the last full moon. Now, the dial is accurately set and will indicate the proper moon phases as long as the clock operates continuously without interruption. Be well aware that if the clock stops for 24 hours or longer, then the moon dial will also stop. In this case, it will have to be reset all over again.


Locate and Inspect Click Spring (If Required)

If for some reason the moon dial will not rotate properly, you ought to locate and inspect the clock’s click spring. Facing the clock’s front, remove the top side panel and open the side door. Additionally, you could also remove the rear access panel. You’ll find the click spring at the back side of the moon dial. Now, place your finger at the tip of the click spring. Pull the click spring approximately half an inch away from the saw tooth of the moon dial. Then, carefully release.

If performed correctly, the click spring and dial should snap into proper alignment immediately, enabling for proper functionality. Be sure to never force the click spring if you still feel resistance when trying to advance the moon dial with it in its proper position, as this will damage it.


Check Gear Engagement (If Required)

Finally, if the moon dial still cannot be easily advanced, then it’s an indication that the gears that automatically advance the moon dial are actively engaged. In order to correct this and restore the dial’s functionality, rotate the minute hand backward by three hours.

With diligence, precision, and care to not force components, setting your grandfather clock’s moon dial is a quick and simple procedure. If you’re ever unsure of how to proceed or would like the help of a professional, don’t hesitate to contact us.

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