Introduced at SIHH in 2015, the Duomètre Sphérotourbillon Moon was the sixth model in the Jaeger-LeCoultre Duomètre line. Closely related to the Cal. 382 Duomètre à Sphérotourbillon, this Cal. 389 movement adds a novel moon phase indicator concentric to the hands. This newly-developed moon phase complication is much more accurate than previous models, only needing adjustment after 3887 years.
Until this model, each member of the Duomètre family had been significantly different in design, even though all divide two barrels of power between independent functions of the watch movement. The Sphérotourbillon Moon is very closely-related to the Sphérotourbillon, with one mainspring barrel powering the gear train and complications while the other powers the tourbillon escapement. The Sphérotourbillon is a multi-axis tourbillon with numerous important technical achievements. In addition to the divided “Duomètre” double barrel power system, the Duomètre à Sphérotourbillon uses an unusual cylindrical balance spring and is the first tourbillon to include a stop seconds and zero reset feature for precise time adjustment. The tourbillon rotates on two axes Every 30 seconds around the axis of the balance and every 15 seconds around a second axis, inclined 20º. Cylindrical balance springs have been seen in marine chronometer clocks before but it was not until the Jaeger-LeCoultre Reverso Gyrotourbillon 2 in 2008 that such a spring appeared in a wristwatch. This same concept is used in the Duomètre à Sphérotourbillon, with two terminal Breguet curves, one at each end of the spring.
Although the escapement does not stop as is common with hacking movements, a push-piece at 2 o'clock serves to stop the small seconds hand and bring it back to zero, according to the flyback principle. This had never before been achieved in a tourbillon. By allowing the escapement to continue its motion even as the gear train is stopped, the watch will not suffer from timekeeping fluctuations when the movement restarts.