Jaeger-LeCoultre moon phase watches: the magic of the stars on your wrist

Observing the lunar cycles on a moon phase watch is a unique experience. New moon, first quarter, full moon, last quarter: the lunar cycle is a spectacle as constant as it is fascinating. With its moon phase watches, Jaeger-LeCoultre captures this magic with incomparable elegance.

How does a moon phase watch work?

A moon phase watch is a complication watch that displays the different phases of the lunar cycle. Appreciated for its precision and technical complexity, this display is proof of the unique craftsmanship only possessed by the very best master watchmakers. 

At the heart of the watch sits a disc showing the different phases of the moon. This is positioned behind a moon-shaped window on the dial. This disc rotates thanks to a precise mechanism composed of wheels and gears that mimic the lunar cycle. Most moon phase watches include a corrector to adjust the disc if necessary.

As the weeks pass by, the dial displays the image of the moon and its progression. The moon disc rotates slowly to reflect the different phases, allowing the current phase of the moon to be seen through a small opening or window on the dial.

Mastering the lunar cycle: a precise art

A lunar month lasts 29 days, 12 hours, 44 minutes and 2.8 seconds, or 29.53 days. Most models round this up to 29.5 days, leading to a slight discrepancy. In fact, the difference between a moon phase watch mechanism and the actual length of a lunar cycle usually results in a difference of one day every 2 years, 7 months and 20 days. 

To compensate for this difference, more sophisticated moon phase watches feature a more precise mechanism. The lunar month then lasts precisely 29 days, 12 hours and 45 minutes, resulting in a difference of one day only every 122 years. 

This level of technical perfection is testament to the watchmakers’ commitment to accurately reproducing the celestial dance of the moon, offering a perfect symbiosis between mechanical complexity and astronomical beauty.

The moon phase: a complication showcased by Jaeger-LeCoultre

The moon phase indicator generally completes the perpetual calendar. This is true of the Master Grande Tradition Quantième Perpétuel 8 Jours SQ watch from Jaeger-LeCoultre, equipped with Calibre 876SQ. This complication can also appear on its own, as with the Rendez-Vous Moon watch, fitted with Calibre 935, on which the lunar months are displayed against a starry sky background.