In English, the term blue moon refers to the second full moon within a given calen-dar month, a rare phenomenon that on average occurs only every two and half years. Most mechanical moon-phase indications must be corrected by one day “once in a blue moon”. This is because for simplicity’s sake, they round the period of time be-tween two new moons down to 29.5 days even though it is actually 44 minutes and 3 seconds longer. 

A. Lange & Söhne moon-phase watches are much more precise. Most of them repro-duce the lunar month with an accuracy of 99.998 per cent. The new GRAND LANGE 1 MOON PHASE is one example. Its display only needs to be corrected by one day every 122.6 years. But Lange’s product developers demonstrated that precision can be fur-ther enhanced: The orbital moon-phase display of the RICHARD LANGE PERPETUAL CALENDAR “Terraluna” presented this year is calculated with such accuracy that it takes 1058 years to deviate by one day. Additionally, it shows the constellation of the moon relative to the earth and the sun. 

Since 1994, the manufactory has developed 15 calibres with moon-phase displays. Five models from the current collection that feature this and other complications were photographed against fascinating backdrops: depictions of the universe from the “Harmonia Macrocosmica” set the stage for the highly precise timepieces. They come from the magnificent sky atlas created by German-Dutch mathematician and cartographer Andreas Cellarius in 1660*. The scenography emphasises the affinity between astronomy and horology: in timepieces with astronomical complications, watchmakers have always attempted to emulate the progression of celestial bodies as accurately as possible. 

From today’s perspective, Cellarius’ rich illustrations make it clear how fundamentally our view of the world has changed in the course of the past two millennia: it evolved from Ptolemy’s geocentric standpoint that placed the earth in the middle of the cosmos to the current model of an expanding universe. 

The patent-pending orbital moon-phase display of the RICHARD LANGE PERPETUAL CALENDAR “Terraluna” is a genuine innovation in the domain of precision watch-making. With peerless accuracy, it depicts the changing orbital position of the moon relative to the earth and the sun. It is based on calculations used to determine the orbits and altitudes of planets attributed to Danish astron-omer Tycho Brahe (1546-1601). His observations of planetary positions were the most precise ones in the era before the telescope was invented.

RICHARD LANGE PERPETUAL CALENDAR "Terraluna"

The focus is on the earth's companion in the GRAND LANGE 1 MOON PHASE. The waxing and waning of the moon can be contemplated in rich detail inside the hour and minute circle. A similar objective was pursued by Cellarius with his rendition of the epicycle theory, which was endorsed until the 17th century. It suggests that the moon moves on small circular orbits (epicycles), which in turn progress around the earth along eccentric paths.

GRAND LANGE 1 MOON PHASE

The 1815 RATTRAPANTE PERPETUAL CALENDAR unites the technical fascination of a split-seconds chrono-graph with the enduring precision of a perpetual calendar. The Ptolemaic geocentric system is visible in the back-ground. It postulated that the earth was the immutable centre of the universe until the theory was superseded by the Copernican revolution in the 16th century.

1815 RATTRAPANTE PERPETUAL CALENDAR

The development of the SAXONIA ANNUAL CALENDAR was driven by the desire to achieve clarity and harmony in the arrangement of its many displays. In this scenogra-phy of the planets that orbit the earth, as envisaged by Tycho Brahe, the watch occupies the position of the sun. The Danish astronomer, too, considered the earth to be the rigid centre of the cosmos, around which the sun, the moon, and the stars move along their orbits. However, he believed that all the other planets, the earth being the exception, orbited the sun.

SAXONIA ANNUAL CALENDAR

The DATOGRAPH PERPETUAL is an ingenious combi-nation of a flyback chronograph and a perpetual calendar. Against the backdrop of the Ptolemaic system as por-trayed by Andreas Cellarius, it unites horological compli-cations that keep track of the moment and of perpetuity.

DATOGRAPH PERPETUAL

* Andreas Cellarius, Harmonia Macrocosmica 

With its imaginative cosmic scenographies, the “Harmonia Macrocosmica” sky atlas published in Amsterdam in 1660 by Andreas Cellarius (1596–1665) is one of the most impressive works of art in astronomical history. The celestial charts of the German-Dutch mathematician and cosmographer were reproduced with 29 large-format copper plate prints deemed to be the pinnacle of the golden age of cartography. They show Claudius Ptolemy's geocentric view of the cosmos, Nicolaus Copernicus' heliocentric system, and Tycho Brahe's reconciliation theory as well as the orbits of the sun, moon, and planets, and the constellations of the northern and southern hemispheres. An annotated reprint of “Harmonia Macrocosmica” was published by Taschen GmbH in Cologne in 2006.