News · Jaeger-LeCoultre

Jaeger-LeCoultre maps sidereal time with the Hybris Artistica 945

A five-piece white-gold edition combines a 23-hour, 56-minute Cosmotourbillon orbit with a minute repeater and grisaille-enamel sky.

Hen & Mills Editorial · 3 min read · 10 September 2026

• The Cosmotourbillon orbits the dial once every sidereal day of 23 hours, 56 minutes and four seconds.
• Hand-wound Calibre 945 combines the celestial display with a minute repeater and 40-hour reserve.
• Reference Q5263482 is limited to five white-gold watches and has no announced price.

Jaeger-LeCoultre has revisited its Calibre 945 in a five-piece Master Hybris Artistica that combines a minute repeater, Cosmotourbillon and map of the northern sky. Announced on 9 September 2026, reference Q5263482 uses a 45mm white-gold case and a dial made with grisaille enamel. The tourbillon completes one circuit in a sidereal day, linking the movement's rotation to the celestial display rather than the familiar 24-hour civil day.

A sky measured in sidereal time

A sidereal day is the time Earth takes to rotate once relative to the stars: 23 hours, 56 minutes and four seconds. Calibre 945 makes that interval visible by carrying its flying tourbillon around the dial once per sidereal day. The carriage also turns on its own axis in 60 seconds. Together, those motions put the regulator into the same frame as the northern-sky chart instead of treating it as a separate mechanism at the foot of the dial.

The celestial display shows the constellations visible from the northern hemisphere. A golden sun-shaped pointer gives the time on a 24-hour scale around the dial, while a separate indication covers the civil hours and minutes. Jaeger-LeCoultre also lists the month among the functions. The display therefore brings together three clocks: conventional time, the annual position of the sky and the slightly shorter rhythm of the sidereal day.

Grisaille enamel supplies the depth

The sky chart is executed in grisaille enamel, a technique that builds an image by working pale enamel over a dark ground. Jaeger-LeCoultre says the enamelling alone requires 24 hours of work. The result is not merely a printed star map sitting above the calibre. It gives the dial a layered, luminous field through which the tourbillon and the orbital time display can be read.

The 18-carat white-gold case measures 45mm across and 16.05mm thick. A sapphire crystal caseback reveals the reverse of the hand-wound movement, while a blue alligator strap continues the colour of the dial. Water resistance is rated to 5 bar. These are grand-complication proportions, but the case has a recognisable round Master profile, leaving the unusual mechanics and enamel to carry the visual drama.

Calibre 945 sounds the time as well

The celestial display shares the case with a minute repeater. Activated on demand, the repeater sounds the hours, quarter hours and minutes. Jaeger-LeCoultre's specifications do not turn that into a water-resistant sports proposition or an everyday timing instrument. It remains an acoustic complication within a highly specialised astronomical watch, with the case, gongs and hand-wound movement designed as a complete system.

Calibre 945 runs at 28,800 vibrations per hour, or 4Hz, and has a 40-hour power reserve. The Cosmotourbillon contains 73 parts. Its 60-second rotation can serve the conventional purpose of a tourbillon display while the entire mechanism's 23-hour, 56-minute and four-second orbit carries the astronomical calculation. That double motion is the technical link between the balance and the painted sky above it.

Five pieces keep the premise narrow

This Master Hybris Artistica is limited to five examples. That matters because it is not a broad relaunch of Calibre 945 across the Master collection. The movement has appeared before, but this execution joins it to a specific white-gold case, blue grisaille-enamel dial and a tiny production run. The announcement is best read as a new artistic and material treatment of an established grand-complication architecture.

There is also a useful distinction between what the watch calculates and what it depicts. The movement sets the tourbillon's orbit to sidereal time; the enamel gives that calculation a recognisable northern sky. One is mechanical, the other decorative craft. Bringing them together keeps the complication intelligible. Without the star map, the four-minute daily difference would be abstract. Without the calibrated orbit, the dial would be an illustration rather than an astronomical display.

The minute repeater sits outside that astronomical chain, but it supplies a second way of reading time without looking at the display. That contrast is part of the watch's appeal: one system tracks Earth's rotation against distant stars, while another reduces the present hour and minute to sound. Both depend on careful sequencing inside the same 45mm case.

Master Hybris Artistica Calibre 945 price and availability

Jaeger-LeCoultre has not announced a price for reference Q5263482. Production is limited to five watches, each in white gold with the blue grisaille-enamel celestial dial and blue alligator strap. The manufacture has not published availability details. Any figure quoted without confirmation from Jaeger-LeCoultre would be speculation, so the commercial detail remains officially undisclosed.