Sundial in the Rouffach monastery
The sundial of the Rouffach monastery is located in the former Minorite monastery of Rouffach in Alsace . This sundial has a special feature: it is applied to a wall painting that depicts the world according to a geoheliocentric view of the world .
It probably dates from the 17th century and was restored in 1979.
description
The sundial is on the south facade of the Katharinenkirche, in the cloister of the monastery. This place is not accessible at normal times and therefore cannot be visited. The building and the sundial are listed as a monument historique .
It consists of a mural that is approximately 3.50 mx 3.80 m in size, on which a pole made of metal casts its shadow in the sunshine .
Gnomonic properties
It is a vertical sundial deviating to the west: the direction of the load-bearing wall is rotated by about 37 ° to the west compared to a complete south orientation. It is therefore only illuminated by the sun after 10 a.m. The pole rod is a 1.60 m long iron rod held by a foot that gives it the right direction (parallel to the axis of rotation of the earth).
The clock shows the solar time . Its hourly scale consists only of large Roman numbers arranged around a large circle. These numbers are all aligned with the attachment point of the pole rod, so there is no need to draw hour lines. An astronomical scene is presented within the circle.
This sundial does not have a season scale, although two signs of the zodiac are depicted: Cancer and Capricorn , as symbols for summer and winter. They belong to a floral octagonal frieze that surrounds the entire painting.
The astronomical picture
The astronomical image is in the center of the painting. It shows the world in a geoheliocentric cosmology . The earth sits in the center of the picture, the moon and the sun are drawn on circles that signify their orbits around the earth. Further outwards one recognizes the orbits of the upper planets Mars , Jupiter and Saturn . But the orbits of Mercury and Venus revolve around the sun. The outer limit of the universe is represented by a green circular ring, which symbolizes the sphere of the fixed stars .
A similar world model can be found in Martianus Capella (5th century), Valentin Naboth (16th century) or Andrea Argoli (17th century).
There are 42 stars on the celestial sphere ; 14 of them are precisely marked with their names by radial inscriptions: Mirach in Andromeda, Sirius in Cane Majore , etc. The writings are opposite their declination on an angular scale.
In addition, remarkable diameters or rays are drawn on this drawing and provided with a Latin legend: the world axis (Axis Mundi), the equator ( Equator ), the tropics ( Tropicus Cancri , Capricorni ), the ecliptic ( Linea Ecliptica ), its axis and poles on the polar circles , and finally the border circles of the zodiac strip ( Circulus Excursuum ), which are represented here by rays. Within this last, the zodiac is indicated by two orange-yellow areas.
history
Dating
The geoheliocentric representation of the world and the absence of planets that are not visible to the naked eye suggest that the Rouffacher sundial dates from the 17th century. This hypothesis has not yet been confirmed in any literature. The date August 16, 1617 is written on the gable above the painting. However, this date is wrong, it was written on the basis of a wrong hypothesis during the last restoration.
The 1979 restoration
In 1970 the plaster on which the painting is drawn was in a damaged condition. Image and inscriptions threatened to disappear. An experienced gnomonist , René RJ Rohr, pointed out the damaged condition and obtained a restoration from the responsible authorities to save this historic sundial. The work was carried out in 1979 under his supervision. During this restoration several changes were made to the drawing: the position of the moon and the planets Mars, Venus and Saturn. RJ Rohr was convinced that the picture wanted to show a lunar eclipse that took place in August 1617.
The geographical map
In 2017, examinations of photographs from 1911 made it clear that earlier the painting also contained a geographic map showing at least Europe , Africa and the Middle East . This map was probably painted over by the scrolls of the ornamental frieze during the penultimate change around 1848.
The entire history of the Rouffach sundial and its mural has not yet been depicted; the oldest known writing about it dates back to 1906.
Literature and web links
- René RJ Rohr, La fresque du cadran solaire des Récollets à Rouffach , Cahiers alsaciens d'archéologie, d'art et d'histoire, Volume XV, Strasbourg 1971, pp. 109-115 (French).
- René RJ Rohr, The Riddle of the Franciscan Sundial in Rufach , Writings of the Friends of Old Clocks, Volume XIII, Ulm 1977.
- Lunar eclipse September 23, 2015, July 27, 2018, Dreisamtal, historical information online .
- Alain Bourgoin, Note sur la fresque astronomique de Rouffach (Haut-Rhin). Essai d'Interprétation , 1990 (not published), Archives municipales de Rouffach (French).
- La fresque du cadran solaire des Récollets de Rouffach, Cadran-Info n ° 37 (May 2018), Société astronomique de France . (French).
Individual evidence
- ↑ Entry PM68000329 in Base Palissy of the French Ministry of Culture (French)
- ↑ The pole rod has been adjusted since the 20th century.
- ↑ The planetary configuration from August 16, 1617 does not match the picture. Carte du ciel , Olivier Esslinger.
- ^ RRJ Rohr, L'énigme de la fresque du cadran solaire de l'ancienne église des Récollets de Rouffach , Cahiers alsaciens d'archéologie, d'art et d'histoire, Volume XX, Strasbourg 1977, pp. 129-135
- ↑ Photography: French Ministry of Culture, UDAP Colmar, ref: Drac Grand-Est / UDAP68 / DKM10013, 1911
- ↑ La fresque du cadran solaire des Récollets de Rouffach , Cadran-Info n ° 37 (May 2018), Société Astronomique de France
- ^ Theobald Walter: The Minorite Monastery at St. Katharina in Rufach . In: Journal of the Society for the Promotion of the History, Antiquity and Folklore of Freiburg , (Volume 7 of the New Version, Alemannia ), 1906/07, p. 51. ( Digitized at the Albert Ludwig University of Freiburg).