This unique astronomical demonstration instrument is designed at the Brussels court of CHARLES OF LORRAINE (1712-1780), governor of the Southern- then Austrian - Netherlands. Its creator, the Jesuit JEAN PAULUS (1710-1781), was attached to the physico-chemical cabinet of the prince. PAULUS was fascinated by the regularity of the heavens. He made his first astronomical clock in 1762, but at that time it consisted only of a system of dials with two rotating globes. In 1771 he invented this present instrument, specifically intended for demonstrations. PAULUS added two planetariums, both depicting a different world system. This was shortly after the famous Transits of Venus of 1761 and 1769, which had attracted worldwide attention.

As a Jesuit, PAULUS had to follow the Catholic Church's rejection of the COPERNICUS system, in which the Earth was reduced to an ordinary' planet, instead of being the centre of the universe. However, the Classical world system of PTOLEMY, in which the Earth was literally at the centre, could not explain the widely observed Transits of Venus. Therefore, PAULUS resorted to a little- known alternative, the world system of MARTIANUS CAPELLA, in which the Earth is still central, but the planets Mercury and Venus revolve around the Sun, while the Sun, in tum, (just as the Moon) moves around the Earth. The Transits of Venus could thus be clearly explained, while the Earth's central position in the universe was still maintained. In contrast- and for further explanation and demonstration - PAULUS depicted the world system of COPERNICUS in the other planetarium.

After the sudden death of JEAN PAULUS in 1781, the instrument came into the hands of the Brussels mathematician MICHEL GHIESBREGHT (1741-1827). He, however, mistook the rather unknown system of MARTIANUS CAPELLA for that of TYCHO BRAHE, in which the Sun (and the Moon) revolve around the Earth and all planets revolve around the Sun. GHIESBREGHT, who not only acquired the astronomical clock, but also all its design drawings, subsequently pretended to be the inventor and maker of the instrument. This is apparent from the engraved signature he put on the instrument and from several illustrated descriptions that he sent to various authorities, including Napoleon Bonaparte.

Partly thanks to the fame that the instrument brought him, GHIESBREGHT was appointed professor at the Theresiacollege in Brussels and later also head of the land registry in the Départ de la Dyle, around Brussels.

The instrument displays - among other things-the following (from left to right and from top to bottom):

Within an Armillary Sphere: the only known Planetarium according to MARTIANUS CAPELLA: the Sun and the outer planets revolve around the Earth, but Mercury and Venus revolve around the Sun.
Celestial Sphere-indicates the position of the fixed stars in relation to the Sun and Moon, plus eclipses.
Dial indicating the position and movement of the Moon, including its apogee and perigee
Time dial for 24 hours. The different pointers indicate the civil, astronomical, Roman and Babylonian time.
Large dial indicating several aspects of the position of the planets.
Small dial: position of the planets and the Sun relative to the Earth.
Earth Globe: one revolution every 24 hours, marking the boundary between illuminated and dark areas.
Cartouche indicating the mean solar time, or civil time.
Cartouche indicating the day, week, month and age (phase) of the Moon.
Dial position of Jupiter's moons.
Within an Armillary Sphere: a Planetarium according to COPERNICUS the Earth and all other planets revolve around the Sun. Only the Moon revolves around the Earth.

After GHIESBREGHT's death, this astronomical clockwork has been:

...exposed, between 1830 and 1880, in the Element Géographique in Brussels, a private museum of the geographer PHILIPPE VANDERMAELEN (1795-1869), and his heirs.
owned, between 1903 and 2017, first by the brewer JEAN VANDER BORGHT (1860-1926) and later by his heirs. Between 1921 and 1952 the clock was installed at the country-estate of the VANDER BORGHT family, the "New Castle of Rukkelingen in Sint-Pieters-Leeuw (south of Brussels).
...exposed, as a loan, between 1952 and 2000 in the Broodhuis, the City Museum of Brussels.
.... restored and in part reconstructed, between 2017 and 2022 by PIETER DE RUITER in Epe, on behalf of the new - and current-owner BERT DEGENAAR of Planetarium Zuylenburgh in Oud-Zuilen.

The Astronomical Clock

Jean Paulus (1710 - 1781) & Michel Ghiesbreght (1742-1827)