Patek Philippe Sky Moon wristwatch Ref. 5102 in 18K white gold

Patek Philippe's astronomical Sky Moon Ref. 5102 wristwatch opens up celestial perspectives on its deep blue dial. It shows a precise chart of the sky in the NortHern hemisphere, depicting the steady progression of the stars, the orbit of the moon, and the moon phases. A golden ellipse frames the section of the nocturnal sky as it appears over the city of Geneva. Two slender white hands above the dial indicate the hours and minutes of mean solar time on the twelve-hour scale at the periphery of the watch.
The heart of the sky-moon mechanism is a gear train of truly astronomical complexity. Out of the 25 trillion possible combinations of transmission ratios, Patek Philippe found the one that simultaneously achieves the highest degree of accuracy in depicting the motion of the heavens and in tracking the waxing and waning of the moon. The gear train is based on the mechanism originally developed for Patek Philippe "Star Caliber 2000" pocket watches and then further miniaturized for Patek Philippe "Sky Moon Tourbillon" wristwatches.
The self-winding movement, which incorporates the module with the astronomical functions (Patent CH 688 171 B5), is composed of 301 individual parts that are finished and assembled by hand. It bears the Geneva Seal, the highest official hallmark of watchmaking quality. The 18K white gold case is 9.78 mm high, has a diameter of 43.1 mm, and is water resistant to 30 meters. The Ref. 5102 has two crowns: one winds the watch and adjusts the hands, the other corrects the astronomical indications.