To truly appreciate Jacob & Co.'s latest timepiece, one must first understand its predecessor. “After the first version [Astronomia], we really wanted to connect the watch to the stars,” explains Luca Soprana, watch development specialist at Jacob & Co. who launched the piece in 2014. This enormously complicated watch features a time display and a tourbillon, with representations of the Earth and Moon spinning on spokes around a central axis - all visible under an expansive sapphire dome. The watch bucked the trend among new timepieces, and while attracting admirers from the Swiss watchmaking industry, it also encountered some skeptics in its early days.
Jacob & Co. quelled a lot of criticism with its new Astronomia Sky. It incorporates a sidereal real-time display that tracks the movement of the stars with zodiac indications. Few features stand out more than the sidereal time complication, a feature that only the most complicated and prestigious watches have ever attempted. "The reference in these displays is the planar sky map produced by Patek Philippe and Vacheron Constantin," Soprana said. Planetarium, where all the stars and planets are spinning. "
The star map of the Astronomia Sky is located below the inverted dome above the movement, with moving ovals indicating stars above the latitude of Geneva. The dome rotates imperceptibly, about 1 degree per day, to account for Earth's orbit around the sun, distinguishing a sidereal day (23 hours, 56 minutes, 4.1 seconds) from a solar day. Soprana had to create special planetary gears to accurately represent large decelerations, but it was Arabo's watchmaking method, which Soprana says allowed him to create a star dome that reminded him of the work of the painter Giotto. “The great thing about working with Jacob,” he says, “is that he’s not a watchmaker at all. He’s concerned with the aesthetic quality of the piece and demands things that a technician would never ask for. He demands a completely different approach.