The Astronomia collection stands out among Jacob & Co.'s portfolio of extraordinary timepieces. Perhaps the most interesting features are the four-arm in-house calibers that rotate on their axes beneath the domed sapphire crystal. The company developed these movements specially for the Astronomia collection.
One exceptional model is the fully skeletonized Astronomia Tourbillon. Here, the caliber's first arm holds the tourbillon, which rotates on three axes. The tourbillon takes 60 seconds to complete a rotation on the first axis, 2.5 minutes on the second axis, and 10 minutes on the third axis. An off-center time display sits directly across from the tourbillon. Its dial is also skeletonized and shows the hours and minutes. A patented differential gear system guarantees the time display is always facing the right direction as the movement rotates. Jacob & Co. mounts two small celestial bodies on the other two arms: A hand-lacquered magnesium globe represents the Earth, while a spherical Jacob-cut diamond with 288 facets symbolizes the Moon.
Other fascinating creations include the Astronomia Sky and Astronomia Solar. Both outdo the Astronomia Tourbillon in terms of complications. The Astronomia Sky places the Earth in the middle, where it serves as a day/night indicator. A small seconds has taken its place on the fourth arm. A disc with constellations from the night sky over the Northern Hemisphere sits beneath the movement. This disc takes a full astronomical year (or 365.259635864 days) to complete one cycle. You can view the constellations currently visible in the sky using the oval indicator.
The Astronomia Solar shows the entire solar system. In addition to the gems on the movement's arms, Jacob & Co. decorates the lower disc with semiprecious stones representing the different planets: There's white granite for Mercury, rhodonite for Venus, red jasper for Mars, pietersite for Jupiter, tiger's eye for Saturn, calcite for Uranus, and lapis lazuli for Neptune. If that wasn't enough, this timepiece also boasts a stunning time display that uses the twelve zodiac signs instead of numerals to mark the hours.