The moon phase on the watch is a miniature rendition of this celestial movement as seen from Earth. It is composed of a disc with two identical moons, commonly peeking through a half-circle aperture.

The moon disc has either a 59-toothed gear that advances one notch every 24 hours, and has to be corrected every 3 years, or a 135-toothed gear that is accurate for 122 years. The moon disc rotates in accordance to the lunar cycle. 

Also see: The difference between an annual and a perpetual calendar 

Heavenly bodies

H. Moser & Cie. has made a couple of improvements to the complication. Firstly, the HMC 801 manual movement features a moon phase system fitted with an intricate wheel that is so precise the discrepancy is a negligible 0.23 seconds per day, or one day deviation after 1,027.30 years! It is one of the most accurate moon phases, if not the most, available on the market.

Secondly, the independent watchmaker has chosen to showcase the moon phase via a large round window at ‘6’ on a completely blank dial. This allows all attention to be directed to the moon in all its splendour.

To give it a more mysterious allure, one of the dial options is Vantablack, a dark substance composed of carbon nanotubes used in telescopes and army thermal camouflage. The nanotubes are vertically aligned next to one another and absorb almost 100% of light, making the dial the blackest ever produced in horology. This gorgeous black dial is paired with a steel case.

Just as appealing is the midnight-blue fume dial, its soothing luster lends a surreal backdrop for the moon. This dial is matched with a red gold case.

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