SIHH 2014: Richard Lange Perpetual Calendar Terraluna Written byWatchTimeJanuary 21, 2014 There is never any doubt about which watch is A. Lange & Söhne’s “hero” each year at SIHH. The brand presents it proudly in the center of its booth, scaled up to proportions even Panerai would not dream of. This year, it is the Richard Lange Perpetual Calendar Terraluna, though CEO Wilhelm Schmid told us that the 1815 Tourbillon gave the Terraluna a run for its money. The Terraluna features an orbital moon-phase display, a perpetual calendar with the Lange outsize date, a 14-day power reserve, and a constant-force escapement. The case measures 45.5-mm x 16.5 mm, and the dial is a regulator style. The large minute circle is at the top of the dial. The smaller dials for the hours and seconds are beneath it, shifted toward the right and left, as with the Richard Lange Tourbillon“Pour le Mérite” presented in 2011. Beneath the characteristic Lange outsize date, two smaller apertures show the day of the week on the left and the month on the right. The leap-year indication is located in a small round window on the right-hand side of the 15 of the minute circle. All displays of the calendar switch instantaneously. To keep the power requirement for the switching as low as possible, the required energy is gradually built up via a cam and then released abruptly at midnight. Lange claims this as a world first for a wristwatch. The display consists of three discs. The celestial disc is decorated with 2,116 stars. Lange says the sky is a fantasy and does represent the sky over any part of the Earth. The moon – visible through a round aperture – orbits around the earth counter-clockwise once a month. The mechanism reproduces the synodic month of 29 days, 12 hours, 44 minutes, and 3 seconds so precisely that it takes 1058 years before the display needs to be corrected by one day. Beneath it, the lunar disc rotates, featuring two round new moons. The progression of the moon phases can be observed through the aperture in the celestial disc. In the constellation view, the position of the sun is occupied by the balance wheel. On new-moon days, the dark moon stands between the earth and the sun. It appears as a bright sphere on the opposite side of the earth on full-moon days. With two mainsprings, the twin barrel delivers a power reserve of 14 days. When a spring barrel stores so much energy, special technical precautions must be taken to keep the rate of the watch stable during the entire power-reserve period. The torque of the fully wound spring would be too high to be delivered directly to the going train. And as its torque declines when it approaches the unwound state, the accuracy of the watch would deteriorate. An elaborate constant-force escapement compensates for both phenomena. In ten-second intervals, it releases an identical portion of the available energy to the balance, thus assuring that the torque remains constant. At the 6-o’clock position, a power-reserve indicator in the form of a circumferential ring tells the owner when the time has come to replenish the movement with fresh energy via the winding crown. The pink gold version will retail for 185,000 euros, and the white gold version will be 186,000 euros. This piece is not a limited edition, but it will be limited by production.