Andreas Strehler Sauterelle à Lune perpétuelle 2M – The Most Precise Lunar Phase Wrist Watch

Unveiled at Salon QP Exhibition 2014 in London, the Sauterelle à Lune perpétuelle 2M by Andreas Strehler is the most precise moonphase wristwatch ever built.

At Basel World 2014, the award winning master watchmaker Andreas Strehler presented his Sauterelle à Lune perpétuelle with a practically perpetual indication of the phase of the moon. Now, he has built an even better moon phase: the Sauterelle à Lune perpétuelle 2M . On 20th July 2014, right on time for the 45th anniversary of the moon landing, the first watch was complete.

The phases of the moon have always fascinated mankind. Luna in Latin and still feminine in many languages, the moon governs the tides, sowing and harvesting. Unfortunately, the lunar phase cycle is it is not in sync with our calendar: On average, it is 29.530588 days. Hence, for a precise phase of the moon, watchmakers would need cog wheels with fractions of teeth – which doesn’t look good and doesn’t work either.

If the Sauterelle à Lune perpétuelle had to be corrected every 14’189.5383 yeas by one day, Andreas Strehler managed to improve this value significantly: The Sauterelle à Lune perpétuelle 2M needs such a correction only every two million years – hence the designation 2M. To be quite precise, the correction is needed every 2’060’757 years.

Based on calculations made by Professor Robert Baggenstos, Andreas Strehler designed a completely new gear train for the 2M. Professor Baggenstos has calculated the ratio and Andreas Strehler has turned these calculations into a gear train. For this, the available space inside the movement had to be reallocated and the position of the balance had to be adapted.

All this was done while the size and design of the present Lune Perpétuelle remained unchanged.  In spite of the improved precision of the moon phase indication, Andreas Strehler managed to keep the number of components the same. Like the Sauterelle à Lune perpétuelle presented in Basel earlier this year, the Sauterelle à Lune perpétuelle 2M only needs four components to achieve this feat.

The Sauterelle à Lune perpétuelle 2M by Andreas Strehler is therefore the most precise phase of the moon ever built. And by some margin: About 2.045 million years. This timepiece has also won the Guinness world records as the most precise lunar phase wristwatch.

Technically, the Sauterelle à Lune perpétuelle 2M is based on the Sauterelle watch by Andreas Strehler. Like the Sauterelle, the 2M has Andreas Strehler’s unique Remontoir d’égalité. This provides a constant supply of energy to the escapement.

The Lune Perpetuelle 2M is a further example of Andreas Strehler’s technically mature constructions. Using only four components, Andreas Strehler achieves the precision of his moon phase indication by driving it continuously instead of switching it forward once a day. By a clever combination of internal and external toothing as well as by the use of prime numbers for the numbers of teeth in the cogwheels, Andreas Strehler could represent complex fractions by cogwheels having integral numbers (halve a tooth on a cogwheel does not work in horology – or in general, for that matter). All this leads to the unprecedented precision of the moon phase indication of the Sauterelle à Lune perpétuelle 2M.

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