News August 2007


The most accurate clockwork planetarium-tellurium
of its kind

The Watch Quote™ - August 28th, 2007

Of the Planetarium-Tellurium.

The Richard Mille Planetarium is a rare and unique object of its kind, containing a vast number of extremely precise indications and astronomic representations within the limits of mechanical design. It was developed to be effective and practical in daily use with the possibility of corrections for different time zones and ease of setting, all of which is executed with workmanship of an extraordinarily high level. All these conditions mean that it is an extremely difficult object to create, and thus a rarity. For this reason more than 8 years have been necessary for the development of the Richard Mille Planetarium-Tellurium.

Another unique aspect of the Richard Mille Planetarium-Tellurium is the addition of a perpetual calendar to the astronomic representations in combination with a détente chronometer escapement. The addition of a highly accurate going train and winding barrel of the planetarium to this escapement make this the most accurate clockwork planetarium-tellurium of its kind.

Description of the Richard Mille Planetarium-Tellurium movement

Despite its enormous complexity, the Richard Mille Planetarium-Tellurium is designed to be:
  • easy to understand
  • easy and practical in use
  • precise and reliable

This means that for the first time, an object of this type will be able to be operated by someone who is not a specialist.

Understandable visual representation

First of all, the diameter of the earth has for practical and aesthetic reasons been notably enlarged in the Planetarium-Tellurium (in reality, the earth is 109 times smaller than the sun) allowing a good view of the continents and indeed of countries. All the planets can be seen perfectly, although these, as explained above, are not to scale regarding size and distance. The indications (date, equation of time, zodiac) are represented in an easily readable and consistent way, and on a separate area from the layout depicting the rotation of the planets.

Practical in use

The planetarium-tellurium is wound with a lever system, and it has a power reserve of 15 days.

The perpetual calendar, which is for the first time included in a planetarium, is fitted with a rapid corrector that allows it to be corrected either forwards or backwards. The same adjustment can be made to the Planetarium-Tellurium, after it has not been wound for a long period. This synchronisation, seemingly simple yet a true technical feat since it is also linked to the time zone mechanism including local, summer and winter time, is the result of lengthy research into mechanical engineering and of very important developments allowing the object to be quickly restarted. This had previously been impossible, because it required asking the help of a specialist in watchmaking and astronomy

The movement is fitted with a Stop-Restart balance whose function it is to restart it after having been immobilised (the problem of the failure of the balance starting up during winding of the movement is an inherent feature of the detent escapement).

Precision and reliability of the Richard Mille Planetarium-Tellurium

The numerous calculations required for this project were executed by a renowned astronomer-physicist. This means that the main consistent error occurs only regarding the earth on its axis, with +1° in approx. 7.7 years. The other figures are as follows: +1° in approx. 168 years for the rotation of the moon around the earth, and -1° in approx. 2 million years for the rotation of the earth around the sun. Given that the value of 1° is below the timing tolerances (+/- 2°) adopted for this planetarium, whilst for the earlier planetariums, the error range was far greater, one realises that the error of the earth on its axis is perfectly acceptable, indeed of no significance.

For the basic movement

The movement of the Richard Mille Planetarium-Tellurium has a detent escapement which is much more efficient than the lever escapement because it interferes less with the balance wheel.

The adjustment forward and backward is done on the balance wheel with variable inertia, using adjusting screws. This type of balance is highly sophisticated and guarantees greater reliability as well as better chronometric results. The index has thus been left out, which allows for a more precise and repetitive time adjustment.

The winding spring is a Tensator type spring, and provides a more consistent torque, which is a vital element in the performance.

Représentations and indications

Astronomic representations (R) and indications (I)
  • Rotation of the earth on its axis (R)
  • Rotation of the earth around the sun (R)
  • Obliquity of the earth (R)
  • Rotation of the moon on its axis (R)
  • Rotation of the moon around the earth (R)
  • Phases of the moon (I)
  • Equation of time (I)
  • Mercury (R)
  • Venus (R)
  • Sun (R)


Rotation of the earth on its axis (R)
One rotation on its axis in 24 hours. Error: +1° in 7.7 years

Rotation of the earth around the sun (R)
One rotation in 1 year. Error: -1° in 2 million years. This rotation is used as the basis for indicating the seasons, the equinoxes, solstices and zodiac signs, represented in their respective windows.

Obliquity of the earth (R)
Exact rotation, the tilt of the earth’s axis between the two poles: 23.5°. This tilt towards the sun provides a perfect understanding of the phenomenon of the seasons.

Rotation of the moon on its axis and rotation of the moon around the earth (R)
The calculation of the rotation is based on a synodic month of 29.53058912 days (time interval between two new moons). Error : +1° in 168 years.

Phases of the moon (I)
The phases of the moon are represented on the moon itself with a surrounding ring that represents the area visible from the earth.

Equation of time (I)
The equation of time is represented by a fuel gauge liek dial divided into sectors on the front part of the planetarium. The hand represents in + or – the minutes that must be added or subtracted from the mean time in order to obtain the true solar time.

Solar time
Associated with the equation of time, it represents the true time in relation to the sun. This indication is connected to the planetary mechanism and is on the dial.

Mercury (R)
Representation of Mercury performing a rotation around the sun in 87.9 days. Mercury does not rotate around its axis.

Venus (R)
Representation of Venus performing a rotation around the sun in 224.7 days. Venus does not rotate around its axis.

Sun (R)
Static representation of the sun in the centre of the planetarium-tellurium.

Time indications
  • Hour
  • Minute
  • Time zones
  • Date (Perpetual calendar)
  • Day (Perpetual calendar)
  • Month (Perpetual calendar)
  • Year, decade (Perpetual calendar)
  • Leap year
  • Power reserve
  • Seasons, equinoxes, solstices, Zodiac signs

Materials used

Titanium, steel, brass, gold, silver, tungsten

Serviceable life
It is still possible today to restore watches that are more than 6 centuries old. The Richard Mille planetarium-tellurium will not be an exception to this rule, each component can be manufactured again. But by way of an example, the mainspring is designed to last approximately 350 years….

Cleaning is recommended every 5 years.

After-sales service
In-house service. In the long term, this type of objects can be repaired by a highly qualified watchmaker, or by a very skilled restorer of ancient watches.

3 years, components and workmanship, including transport. Does not cover drops, extreme shocks or inappropriate handling.

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The Richard Mille Planetarium-Tellurium will be unveiled at The Hour Glass' Tempus Event on the 4th September 2007


From the earliest times of civilization, man has always attempted to duplicate, depict and reflect the surrounding visible celestial universe. These representations could be monumental and static, such as architectural models or temples dedicated to connecting a specific place with specific astronomical determinations, or more portable, mechanical representations of the physical movements of the sun, earth, moon and the planets as well as other types of astronomic occurrences.

One of the first major references to such a man made device depicting the movements of the moon and planets dates from a text by Cicero, which describes an invention created by Archimedes (287-212 B.C.). Although the actual object the text describes was never found, the famous Antikythera, a later machine tentatively dated between 80 and 50 B.C. must surely be the earliest planetarium of its kind. Discovered in 1901 along with a vast number of glass and bronze statues and artefacts, the secret mechanism it contained, able to show the movements of the sun, moon, and four of the planets visible to the naked eye, were only uncovered after X-ray photography revealed the inner workings contained within its green discoloured bronze exterior in 1959.

Many different forms and versions of astronomic machines depicting the movements of the heavenly bodies were created in the course of time in many different cultures. For our purposes, broadly speaking, these can be divided into two major groups: manually set or clockwork driven representations.

One of the earliest European paintings of a geared mechanism representing the movements of the sun, earth and moon with a horizontal layout similar to late 17th century table sized examples, can be seen in a portrait of the German astronomer and inventor Wilhelm Schickard (1592 – 1635) who taught at Tübingen. Quite crude in design and lacking the correct number of teeth for a true representation, the manually driven mechanism he holds in his hand depicts the annual and diurnal revolutions of the earth according to the Copernican model. Be that as it may however, the Tellurium, which is a three dimensional model depicting the earth’s yearly cycle around the sun, its diurnal movements and its parallelism of axis seems to have developed first in The Netherlands and fine examples of Telluriums created by the famous cartographer Wilhelm Janszoon Blaeu (1571-1638) support this history.

However, the development of the clockwork driven planetarium or tellurium that could show the movements of heavenly bodies automatically without manual intervention had to wait until the appearance of newer and more accurate types of escapements that evolved during the course of the 17th century. In addition, there was still much to additional work be done to improve representational accuracy since the calculations of the gear teeth ratios were still imprecise, therefore making it necessary to re-synchronise a planetarium every fortnight (for example, a + 1° error in 8 hours in the rotation of the earth on its axis corresponds, in 15 days, to a + 45° discrepancy).

From a more general perspective, it is perhaps important to recall that from the 14th century until roughly mid 20th century, horology and the applications derived from it were as important to the scientific, military and civilian spheres as are, for us today, information technology and its applications. For this reason, countries such as Italy, Germany, Japan, France, England, and finally Switzerland, competed with each other for supremacy in horology.

Some important names in the field of horology who were occupied with the development of the planetarium are: Han Kung-Lien (ca. 1088), Giovanni de’ Dondi (1318-1389), Jost Bürgi (1532-1592), Willem Janszoon Blaeu (1571-1638), Christian Huygens (1629-1695), Thomas Tompion (1639-1713), Georges Graham (1673-1751), Philip-Mathaus Hahn (1739-1790), Jean-Baptiste Cattin (1688-1767), Antide Janvier (1751-1835), François Ducommun (1763-1839), Jean-Jacques Lepaute (1775-1830), Zacharie Raingo, Pouvillon (1910-1969)

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