The Triple Axis Tourbillon Goes Sidereal

In 2014, Jacob & Co had already stunned the watch industry with the launch of the Astronomia Gravitational Triple Axis Tourbillon. This year, it takes the challenge even further with the Astronomia Sky by adding a never-before-seen complication: a sidereal display in three dimensions combined with an oval sky indicator and a 24-hour day and night display. To understand the complexity of this feat, each innovation will be examined individually.

Sidereal Time

Covering the internal surface of the Astronomia’s case, the celestial dial accomplishes a full rotation in one sidereal year –which is the actual time it takes the earth to make one full rotation around the sun in relation to the xed stars. The blued grade 5 titanium dial features 18K gold stars as well as applied and hand-engraved and zodiac signs.

Oval Sky Indicator

Above this celestial dial is the Oval Sky Indicator, which shows the portion of the stars visible from the Northern Hemisphere. This indicator makes one full rotation in one sidereal day. A sidereal day is how long it takes for the earth to rotate once on its axis: 23.5640916 hours.

Day/Night Indicator

In the center of the satellite axis, a lacquered hand-engraved titanium globe rotates on itself inside a tinted half- domed sapphire, symbolizing night and day.

Satellites Race

Rotating around the watch are the four satellite arms, which rotate around the dial every 20 minutes, so when you look at the watch, it will never appear exactly the same.

On one of the satellites is the amazing triple axis gravitational tourbillon, which rotates on one axis in 60 seconds, on the second axis every ve minutes and around the dial every 20 minutes.

On another satellite is the time (hours and minutes) subdial. Thanks to a clever di erential gear system, the time display is always in the correct position while it rotates around the dial, in other words, the 12 is always up.

On the third satellite is the Orbital Second Hand, an open-worked titanium wheel that rotates in 60 seconds with a second hand, and it also rotates around the dial every 20 minutes.

On the fourth and nal satellite is the patented “Jacob Cut” red moon, a spherical orange sapphire with 288 facets. This sapphire, the rst of its kind in the modern jewelry industry, rotates on its axis every 60 seconds and turns around the dial every 20 minutes.

Optimized Setting

Jacob & Co. found a simple solution to the setting of this complicated timepiece. The Astronomia Sky has two bows and two wheels on the back of the watch, making setting easy. One bow is for setting the time and the day/ night indicator (both based on 24-hour solar time), while the other bow is for winding the mechanical movement. One of the wheels is to set the sidereal time, and the other wheel is used to set the oval sky indicator.

Jacob & Co., known for its unique and captivating complications, has done it again with the Astronomia Sky.