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International Astronomical Union

Category of Astronomical Heritage: tangible immovable
Mannheim Observatory, Germany

Format: IAU - Outstanding Astronomical Heritage Description


Geographical position 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
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    Author(s): Gudrun Wolfschmidt

Old Observatory (Alte Sternwarte) Mannheim (Bus stop "Mensa am Schloss")
since 1880 Karlsruhe.
See also: 1898 Heidelberg-Königsstuhl


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Latitude 49.486739 N, Longitude 8.459715 E, Elevation 97m above mean sea level.


IAU observatory code 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
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    Date: 2021-05-29 15:49:42
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Description of (scientific/cultural/natural) heritage 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
    Entity: 197
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    Date: 2021-09-03 17:42:42
    Author(s): Gudrun Wolfschmidt

Steps of Development

  • before Mannheim: Schwetzingen Observatory (1761, 1764--1775)
  • Kurpfälzische Sternwarte Mannheim (1772--1880)
  • Karlsruhe (Valentiner) (1880--1909)
  • Max Wolf - Privatsternwarte Heidelberg (1880)
  • "Großherzogliche Bergsternwarte", Königstuhl Heidelberg (since 1898),
    today Landessternwarte Königstuhl (LSW)


Christian Mayer (1719--1783) in Heidelberg, Paris, and Schwetzingen

Jesuit astronomer Christian Mayer (1719--1783) (Wi

Fig. 1a. Jesuit astronomer Christian Mayer (1719--1783) (Wikipedia)

Mannheim Observatory next to the Jesuit church (Wi

Fig. 1b. Mannheim Observatory next to the Jesuit church (Wikipedia, CC3, PQ3)


Jesuit astronomer Christian Mayer (1719--1783) studied theology and natural philosophy in Mainz, and became a Jesuit. In 1752, Mayer got the call to the newly founded chair for natural philosophy (experimental physics) at the University of Heidelberg. He set up a physical cabinet in the old university and gave lectures there on physics, chemistry, mineralogy, and astronomy.


Planetarium, George Adams of London (1748/57), in

Fig. 2a. Planetarium, George Adams of London (1748/57), in the Library of the Elector (Kurfürst) Karl Theodor in the Castle in Mannheim (1759) (Bayerisches Nationalmuseum)



In July 1757 he was sent to Paris as a physicist to learn about the art of hydraulics and astronomy. The reason for this was that the residency Mannheim needed a functioning water supply system; Paris was the great role model at the time. During this five-month stay, Mayer also met the astronomers Joseph Jérôme Lefrançois de Lalande (1732--1807), César-François Cassini de Thury (1714--1784), Nicolas-Louis de Lacaille (1713--1762) and Pierre Bouger (1698--1758). They showed him the observatory belonging to the Jesuit order and the Royal Observatory in Paris; there Mayer was trained in observing with astronomical and surveying instruments.



Quadrant, Canivet of Paris (Repsold 1907)

Fig. 2b. Quadrant, Canivet of Paris (Repsold 1907)

Mayer brought from Paris a second pendulum clock, made by Jean-André Lepaute (1720--1789), and a quadrant for horizontal and vertical measurements, made by Jacques Canivet (1714--1773). With both instruments he wanted to make stellar observations in Heidelberg and Schwetzingen as well as a survey of the Electoral Palatinate.

Small Electoral Palatinate Map, Mannheim 1771 (Tec

Fig. 3. Small Electoral Palatinate Map, Mannheim 1771 (Technoseum Mannheim)

For the national surveying project, he later ordered a ruler (Toise) and a graphometer from Canivet in Paris. One result of his meticulous cartographical measurements were the the maps, Basis Palatina (1763) and Charta Palatina (1770), which accurately reproduced the territory of the Electoral Palatinate between the cities of Heidelberg, Mannheim and Schwetzingen.

Mayer’s First Observatory in Schwetzingen (1761, 1764--1775)

Transit of Venus (1761), observed by James Ferguso

Fig. 4. Transit of Venus (1761), observed by James Ferguson (1710--1776) (Wikipedia)

For observing the Transit of Venus (1761) (Wolfschmidt 2013), a wooden structure was erected in front of the orangery in the palace garden of Schwetzingen Castle. Christian Mayer and Elector Carl Theodor observed the Transit of Venus with the Canivet quadrant in the early morning, but "the weather was pretty foggy".

Schwetzingen Observatory on a porcelain plate (Bav

Fig. 5. Schwetzingen Observatory on a porcelain plate (Bavarian National Museum Munich)

Christian Mayer, who was appointed court astronomer in 1762 with an annual salary of 200 guilders, was able to get Prince Elector Carl Theodor (1724--1799) to build a small observatory on the roof of Schwetzingen Palace.

An "observation building" ("observations-gebäu") was erected on the roof of Schwetzingen Castle. This observatory consisted of a wooden turret with an inner diameter of 3.25m with a movable copper roof. It was finished in January 1764, and Mayer was able to use it for surveying, he measured the geographical latitude and longitude of Schwetzingen: Latitude 49°23’4.5’’, Longitude 26°18’30’’ (the zero meridian at that time was El Hierro on the Canary Islands). Thus, Schwetzingen became one of the few geographically well defined places in Europe. Mayer and Carl Theodor observed also a partial solar eclipse from Schwetzingen (August 16, 1765). The Schwetzingen Observatory with the Lepaute clock and the Canivet quadrant remained in operation until the opening of the new observatory in Mannheim. Afterwards, it was completely dismantled; only the copper roof was transferred to Mannheim observatory.

For the next Venus Transit 1769, Mayer was invited by the Imperial Russian Academy of Sciences in St. Petersburg for observation. He transported in his luggage  the most modern and expensive astronomical equipment of the time: a precision pendulum clock with compensation pendulum by the London clockmaker Eardley Norton (1740--1794), an achromatic telescope with a heliometer (a special measuring device for solar observations), made by Peter Dollond, two more telescopes and his Canivet quadrant. All of these instruments have survived until today.
On June 3, Mayer observed the transit with the astronomers and mathematicians Anders Johan Lexell (1740--1784), Leonhard Euler (1707--1783) and Sergej Kotelnikow (1723--1806). Since the celestial event took place in northeast Europe in the evening, only the beginning of the transit could be observed in St. Petersburg. Mayer recorded a time of 1 hour 55 minutes 44.3 seconds. The entire transit took a total of 6 hours 9 minutes.
In August / September 1769 in St. Petersburg, Mayer observed a comet, which Charles Messier had discovered on August 8, 1769.

Mannheim Electoral Palatinate Observatory (1772--1880)

After staying in St. Petersburg for over a year, Mayer returned to Heidelberg and Schwetzingen in September 1770. He had used the return trip to visit the observatories and their leading astronomers in Åbo/Turku, Stockholm, Copenhagen, Lübeck, Hamburg, Hanover, Göttingen and Kassel, and to exchange ideas about astronomical research and the construction of observatories. Mayer had the ambition to have an observatory built in Mannheim as "Crown of the Electoral Palatinate Cities". Therefore, he tried to convince the elector with a memorandum to build a new observatory, which he presented to him on New Year’s Eve (1771).

Mannheim Observatory, design by Johann Lacher, aro

Fig. 6. Mannheim Observatory, design by Johann Lacher, around 1772 (Heidelberg University Library)

In this multifaceted, detailed treatise, which also included plans, Mayer came to the conclusion that the most favorable location for the new observatory must be near the Mannheim court. Since the first plans to set up these in one of the palace pavilions or in the old Jesuit seminar next to the court church, due to static problems, did not prove to be feasible, a plot of land near the wall behind the Jesuit church was chosen.

Francesco Rabaliatti (1714--1782), the Italian Court architect of the elector, initially entrusted with the designs for the observatory, had tried as thrifty  as possible to fulfill Mayer’s wishes. Since Rabaliatti insisted on a round or square tower, whereas Mayer insisted on an octagonal tower, Mayer finally had his ideas implemented by fortress engineer and Artillery Lieutenant Johann Lacher († 1775). The octagonal structure has a long tradition for observatory buildings since Antiquity until Baroque time (Wolfschmidt 2021).

On October 1, 1772, the foundation stone of the new observatory was laid in the presence of the President of the Electoral Palatinate Academy of Sciences, Baron von Hohenhausen. According to calculations by the contractor Schlichterle, the entire construction cost around 19,000 guilders. The Jesuits advanced part of the costs, 8,000 guilders, which were later repaid to them.

In 1774, the court chamber started to take over the costs for the observatory. With all the later equipment of instruments, the observatory had devoured the enormous sum of 83,000 guilders. In relation: a worker in the Frankenthal porcelain factory earned 20 guilders a month. So he would have had to work for it for more than 345 years.



Elevation and cross-section of Mannheim Observator

Fig. 7. Elevation and cross-section of Mannheim Observatory, Wilhelm von Traitteur, around 1791 (REM Mannheim)


When in late 1775 the most important and largest instrument, the wall quadrant by John Bird from London, arrived at the observatory and was fixed to the wall of the large observing room towards the south, the building was finished, and the astronomers Christian Mayer and the mathematician Johann Metzger lived there.

The 33m high, octagonal tower, which four main sides are oriented towards the four cardinal directions, could be entered through the main portal from the west. It leads to the high and spacious ground floor, from where two further doors opened to the south to a small garden and to the north to a farm yard. To the east is the staircase that connects the five floors of different heights.

The astronomer’s apartment was on the first floor, designed for one person, as Catholic religious members were assumed to be the residents of the building. The apartment consisted of a small kitchen, a living room, a bedroom and a writing room. Above the apartment was the astronomer’s study, the large, approximately 9.80m high observing room with the most important astronomical instruments, the telescopes, quadrants, globes and pendulum clocks. In front of the high glass doors, there are balconies to the north, west and south, only not to the east, because there was the staircase and in addition, the choir of the Jesuit church obscures part of the sky.

Above this room was a floor reserved for external astronomers and guests as well as a small scientific library. Above, as the last room under the platform, there was again an observation room with a ceiling height of 5.90m, and balconies in front of the French windows. In August 1778, a zenith sector, made by Jeremiah Sisson (1720--1783) of London, was installed with a small gallery in this observation room, which is unfortunately rarely used.

Mannheim Observatory with the turret on the platfo

Fig. 8. Mannheim Observatory with the turret on the platform (Photo: Kai Budde)

In order to be able to observe stars in the zenith, there was a circular, lockable hatch in the platform of the tower. On the platform, which is surrounded by a walled parapet, there was a small turret in the center with a movable copper roof, which was also intended for astronomical observations; it was the roof of the Schwetzingen Castle Observatory.

View from the platform of the observatory to the n

Fig. 9. View from the platform of the observatory to the north, around 1790 (REM Mannheim)

Mayer’s astronomical research

In September 1777, Mayer completed a first series of observations on what he called "fixed star satellites", today called "double stars". He presented his results to the academies of London, Paris and Philadelphia, which praised it. Then he published his research in 1777 under the title: "100 Begleiter von Fixsternen und deren ausgezeichnete Verwendung zur Bestimmung der eigenen Bewegung der Fixsterne" (100 companions of fixed stars and their excellent use for determining the own movement of the fixed stars). A published dispute arose over the technical terms used in this book with the Viennese astronomer Maximilian Hell (1720--1792). Mayer decided to write a defense "Gründliche Vertheidigung neuer Beobachtungen von Fixsterntrabanten, welche zu Mannheim auf der Sternwarte entdeckt worden sind" (Thorough defense of new observations of fixed star satellites that were discovered at the Mannheim observatory in 1778).

Based on his observations and calculations, for example on the fixed star Arcturus in the constellation Bootes, Mayer had concluded that the fixed stars and their planet-like companions were moving. Today we know that this phenomenon is mostly about distant suns orbiting each other.

Commemorative medal for Christian Mayer 1783 (Tech

Fig. 10a. Commemorative medal for Christian Mayer 1783 (Technoseum-Mannheim)

Christian Mayer’s Double Star Catalogue (177

Fig. 10b. Christian Mayer’s Double Star Catalogue (1779)

In addition to the fixed stars, Mayer devoted himself to the Sun and our planetary system. Here especially he observed the phenomenon of sunspots, the planets Mercury, Venus, Mars (he believed he could see channels), Jupiter with its four large moons and Saturn, whose rings he did not yet recognize as such (the telescope optics were still too weak and therefore called it "handle".

The northern lights (aurora borealis), which could also be seen in Mannheim at that time, attracted his particular attention, and he measured the unusual fluctuations in the magnetic lines.

Mayer was a member of several respected learned societies, and was in contact with astronomers in Munich, Vienna, Budapest, St. Petersburg, Paris, Marseille, London, Copenhagen, Stockholm, Bologna, Padua and Göttingen. In 1780, Mayer’s colleague Johann Metzger died, who had helped Mayer significantly with the fixed star observations and with the calculation of the aberration and nutation of a total of 352 fixed stars.



  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
    Entity: 197
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    Status: PUB
    Date: 2021-08-06 21:26:24
    Author(s): Gudrun Wolfschmidt


Model of Mannheim Observatory in the Technoseum, w

Fig. 11a. Model of Mannheim Observatory in the Technoseum, wall quadrant and astronomical instruments (Photo: Gudrun Wolfschmidt)

The largest and heaviest instrument in the observatory was the wall quadrant, made by John Bird of London in 1775, with a radius of 2.50m (eight English foot). It cost 400 English guineas, which was the equivalent of about 4,000 guilders. With the wall quadrant, Mayer and Metzger began their fixed star observations in 1776.

The large wall quadrant, made by John Bird of Lond

Fig. 11b. The large wall quadrant, made by John Bird of London, 1775 (Technoseum Mannheim)

Thanks to continued inventories between 1776 and 1983, we are well informed about the instrumention. They offer a very detailed picture of the acquired, borrowed and repaired astronomical instruments. They provide information about the manufacturers, the agents who helped with the purchase and the prices. The first inventory was made by Mayer in 1776. At that time, it already listed 41 instruments, including those from the Heidelberg University’s Physics Cabinet (Mayer was in charge of it).

Heliometer attachment, Peter Dollond of London, ar

Fig. 12. Heliometer attachment, Peter Dollond of London, around 1769 (Technoseum Mannheim)

In March 1880, the Mannheim Observatory was relocated to Karlsruhe; the last inventory made in Mannheim by Valentiner listed the following instruments in 1876:

List of Instruments (1876)

1.    Refraktor von Steinheil (mit diversen Zubehör a--t)
2.    Passageinstrument von Ramsden von 1780 (mit Zubehör a-- g)
3.    Der Reichenbach’sche Kreis mit stehender Säule aus dem Jahr 1811 (mit Zubehör a--g)
4.    Der große Mauerquadrant von Bird. Er ist im Jahre 1775 in London verfertigt und ganz von Messing gearbeitet. (mit Zubehör a--f)
5.    Achromatisches Fernrohr von Fraunhofer aus dem Jahr 1817 (mit Zubehör a--f))
6.    Achromatisches Fernrohr von Ramsden, 2 ½ Fuß lang mit messinger Röhre und Stativ und feiner Vertikalbewegung.
7.    Achromatisches Fernrohr von Ramsden 1 ½ Fuß lang mit messinger Röhre und Stativ
8.    Steinheil’scher Cometensucher, angeschafft im Jahre 1859, ohne Stativ
9.    Ein Cometensucher von Fraunhofer aus dem Jahre 1817
10.    ein zehnzölliger Sextant von Troughton
11.    ein 8 ½ zölliger Sextant von Dollond
12.    ein Gregorianisches Spiegelteleskop
13.    ein unachromatischer Cometensucher von Dollond
14.    ein transportabler Quadrant von Sisson. Das Instrument steht mit 4 Schrauben auf einem 3-beinigen Tisch von Eichenholz
15.    eine Pendeluhr von J. Arnold in London mit Compensationspendel von Zink und Stahl.
16.    eine Pendeluhr von E. Norton in London mit Compensationspendel von Messing und Stahl.
17.    eine Pendeluhr von LePaute in Paris mit einfacher eiserner Pendelstange.
18.    eine Pendeluhr von Bob in Furtwangen mit Holzpendel.
19.    ein Boxchronometer von F. Tiede im Holzkasten.
20.    eine silberne Taschenuhr, welche Sekunden schlägt, in einem Etui
21.    eine Standuhr, Federuhr, die nur Minuten zeigt, das Zifferblatt in 24 Stunden eingeteilt.
22.    ein ganz defekter, sogenannter Sekundenzähler; derselbe hat ein blosses Sekunden-zifferblatt und schlägt die einzelnen Sekunden an eine Glocke.
23.    eine kleine Weckuhr.
24.    Ein Ramsden’sches Gefäßbarometer mit messinger Skala und doppelter Eintheilung in französische und englische Maass. Daran ist ein Thermometer mit Rèaumur und Fahrenheit Skala angebracht.
25.    Ein altes Gefässbarometer von D. Quare.
26.    Ein Thermometer von Baumann, mit versilberter Skala, welche Réaumursche und Fahrenheitsche Grade angibt.
27.    Zwei kleine Thermometer mit Skala auf Porzellan nach Réaumur.
28.    ein großes Thermometer mit Skala in Porzellan nach Réaumur
29.    ein großes Thermometer mit Skala in Porzellan in Celsius.
30.    Ein kleines Thermometer mit Skala auf Papier nach Réaumur.
31.    ein künstlicher Horizont von dunkelgrünem Glas mit einer Unterlage von Mahagoniholz.
32.    Ein Astrolabium von Canivet (1765)
33.    ein Astrolabium von Mathias van Os (1589)
34.    ein Ramsdenscher ganzer Transporteur von 9 ½ Zoll Durchmesser, mit Nonius in einem Mahagonikasten.
35.    Ein Kugeltransporteur von 3 ½ Zoll Radius
36.    ein Erdglobus von Vaugondy, ein Himmelsglobus von Vaugondy, Paris1751
37.    eine Ringsonnenuhr von E. Culpeper
38.    eine Sonnenuhr mit Bussole von M. Bergauer
39.    eine Sonnenuhr von Hahn (1777)
40.    ein Heliometerobjektiv von Dollond. (das dazugehörige Fernrohr wird als zerlegt bezeichnet)
41.    ein dreizolliges Objektiv, welches vermutlich zum zerlegten Achromaten von Dollond gehörte.
42.    Kleinteile wie Linsen, Okulare und Werkzeuge.
43.    eine eiserne Toise mit Skala von Canivet Paris 1762
44.    ein altes Kippfernrohr von 2 Fuß 10 Zoll Länge
45.    ein künstlicher Magnet von ziemlich starker Wirkung.

Telescope by Jesse Ramsden, London, after 1775, 40

Fig. 13a. Telescope by Jesse Ramsden, London, after 1775, 400mm focal length and 55mm objective lens (Technoseum Mannheim)

Telescope by Jesse Ramsden, London, after 1775, 77

Fig. 13b. Telescope by Jesse Ramsden, London, after 1775, 770mm focal length and 62mm objective lens (Technoseum Mannheim)

In addition, they also used telescopes by Peter Dollond and Jesse Ramsden equipped with achromatic lenses, as well as small portable quadrants. Mayer particularly liked to use an approximately 60cm long brass Ramsden telescope for observing the four Jupiter moons.

Sisson’s zenith sector built into the upper observation room was specially used to determine the nutation and aberration movements of the stars.

The upper observation room with a wooden gallery,

Fig. 14. The upper observation room with a wooden gallery, precision clock and zenith sector (Model in the Technoseum Mannheim)

At the beginning of the 1780s, when Mayer had cataloged the southern part of the northern starry sky, he wanted another wall quadrant for the observatory and other new instruments to record the missing northern part. The Elector in the meantime in Munich, who was also interested in modern equipment for the Mannheim Observatory, approved further 10,000 guilders in October 1781 for the purchase of a transit instrument, a wall quadrant, and an equatorial sector. Ultimately, however, only the transit instrument was purchased, because the design and equipment of the instrument far exceeded that of a wall quadrant, and subsequently more than replaced the wall quadrant.

In 1785, two years after Mayer’s death, this device was delivered from Ramsden to Mayer’s successor, Father Karl Joseph König. But at first there was no suitable location for the instrument in the observatory, which had to be mounted on two columns on a horizontal axis in a precise east-west direction. The valuable instrument remained in the box until between 1789 and 1791 a special extension with two cabinets was installed on the west side of the observatory, of which the northern one was selected for the installation of the transit instrument.

Large Steinheil Refractor of Mannheim Observatory,

Fig. 15. Large Steinheil Refractor of Mannheim Observatory, 1859 (Wikipedia, Rivi)

The Mannheim observatory gained international reputation through the research of its astronomers during the 105 years of existence:

Directors and Astronomers

  • Christian Mayer (1719--1783), director from 1771 to 1783
  • Johann Metzger († 1780)
  • Karl Josef König († 1809), astronomer from 1784 to 1786, assistant Mathias Kübel (1742--1809)
  • Johann Nepomuk Fischer (1749--1805), astronomer from 1786 to 1787
  • Peter Ungeschick (1760--1790), astronomer from 1788 to 1790
  • Roger Barry (1752--1813), astronomer from 1788 to 1813
  • Maurice Henri (1763--1825), assistant from 1789 to 1794
  • Heinrich Christian Schumacher (1780--1850), astronomer from 1813 to 1815
    (later Altona Observatory)
  • Friedrich Bernhard Gottfried Nicolai (1793--1846), astronomer from 1816 to 1846
  • From 1847 to 1860 the observatory was not manned by any astronomer.
  • Adam Maximilian Nell (1852--1857)
  • Eduard Schönfeld (1828--1891), astronomer from 1860 to 1875
  • Wilhelm Valentiner (1845--1931), astronomer from 1875 to 1880
    (later in Karlsruhe 1880 to 1896, in Heidelberg 1896 to 1909).


Eduard Schönfeld and the Founding of the Astronomical Society (1863)

The 26 founding members of the Astronomischen Gesellschaft (Astronomical Society) were international, as at the beginning of the VAG (Vereinigte Astronomischen Gesellschaft): eleven worked at observatories abroad (Pulkovo, Dorpat/Tartu, Moscow, Warsaw, Lisbon, Marseille, Lund, and Vienna), the rest came from German states (Bonn, Leipzig, Berlin, Königsberg, Mannheim, Tübingen, Speyer, and Frankfurt / Main). The observatories in Bonn, Berlin, Königsberg and Pulkovo were numerically strongly represented.

Eduard Schönfeld (1828--1891), director of the Mannheim Oobservatory, reported on the Dresden Astronomers’ Meeting in 1861:
"Der Zweck derselben war, eine Theilung der Arbeit zu bewirken, da der Stoff der Astronomie sich jetzt so bedeutend mehrt. Schon auf der Naturforscherversammlung zu Bonn hatte man die Verabredung getroffen, die Störungsrechnungen für die kleinen Planeten durch Publication der allen gemeinsamen Rechnungen zu erleichtern. In Dresden beschloß man, die Störungstafeln fortzusetzen, wobei man dieselben auf periodische Kometen ausdehnte, ... Es wurde ferner eine Gleichmäßigkeit in der Behandlung der Beobachtungen beschlossen ... Weitere Verabredungen über Fixsternbeobachtungen und dergleichen in grösserem Massstabe wurden auf eine für das Jahr 1863 in Heidelberg abzuhaltende Versammlung verschoben."
(The purpose of this was to distribute the labor, since astronomy now increases so considerably. At the meeting of natural scientists in Bonn, an agreement had already been made to facilitate the perturbation calculations for the small planets [Gauß theory of orbit determination] by Publishing the calculations. In Dresden, it was decided to continue the perturbation tables, extending them to periodic comets ... It was also decided that the observations should be treated more uniformly ... Further agreements on fixed star observations et cetera in a larger scale were postponed to the year 1863, Meeting to be held in Heidelberg.)
(Schönfeld 1861, hier S.~36. Deutsches Museum Sondersammlung).


"Societas Meteorologica Palatina" -- Meteorology --
in the Academy of Sciences in the Castle of Mannheim

Johann Jakob Hemmer (1733--1790), first secretary

Fig. 16a. Johann Jakob Hemmer (1733--1790), first secretary of the Societas Meteorologica Palatina (Wikipedia)

Hemmer’s <i>Ephemerides Societatis Met

Fig. 16b. Hemmer’s Ephemerides Societatis Meteorologicae Palatinae observationes anni 1789

Hair hygometer (Photo: G. Wolfschmidt)

Fig. 16c. Hair hygometer (Photo: G. Wolfschmidt)

The Societas Meteorologica Palatina (Wolfschmidt 2020) was founded as the third class of the Mannheim Academy of Sciences by Elector [Kurfürst] Karl Theodor von der Pfalz und Bayern (1724--1799) in 1780 and existed until 1795 -- only 200m from the observatory.

The first secretary Johann Jakob Hemmer (1733--1790) set his goals international cooperation as follows:
"Die Wissenschaften, die einen unmittelbaren Einfluss auf des Menschen Leben und seine tägliche Beschäftigung haben, verdienen eine besondere Beachtung, Aufmerksamkeit und Fürsorge. Aus diesen Gründen haben Seine Kurfürstliche Durchlaucht die Witterungslehre ihres höchsten Schutzes gewürdigt und Anstalten treffen lassen, dass an mehreren wichtigen Orten der kurfürstlichen Erblanden, auch in anderen Gegenden Europas und der übrigen Weltteile künftig mit gleichartigen Instrumenten tägliche Beobachtungen gemacht und eingesammelt werden."
(The sciences, that have a direct influence on man’s life and daily activity, deserve special consideration, attention and care. For these reasons, His Elector Highnesses appreciated the weather theory, granted the highest level of protection, and made arrangements that in the future, daily observations will be made and collected with similar instruments in several important places of the electoral hereditary lands, also in other regions of Europe and the rest of the world).

Hemmer’s goal was to standardize the measuring instruments based on the latest developments:

  • Measurement of air pressure: barometer (Torricelli 1643),
  • Measurement of temperature: Thermometer: Fahrenheit mercury thermometer (Danzig 1714), alcohol thermometer by Réaumur (Paris 1730) and Mercury thermometer from Celsius (Uppsala 1742),
  • Measurement of humidity: hair hygrometer (Saussure 1783) and quill pen Hygrometer (Chiminello 1783, Retz 1779, de Luc 1773, 1791),
  • Measurement of the magnetic declination: Declinatorium (Magnetic Association),
  • Measurement of air electricity: gold leaf electroscope (Bennet, Abraham 1787).

Model of the <i>Societas Meteorologica Palat

Fig. 17a. Model of the Societas Meteorologica Palatina in the Technoseum Mannheim, meteorological instruments (Photo: Gudrun Wolfschmidt)

Model of the <i>Societas Meteorologica Palat

Fig. 17b. Model of the Societas Meteorologica Palatina in the Technoseum Mannheim, meteorological instruments (Photo: Gudrun Wolfschmidt)

Model of the <i>Societas Meteorologica Palat

Fig. 17c. Model of the Societas Meteorologica Palatina in the Technoseum Mannheim, meteorological instruments (Photo: Gudrun Wolfschmidt)

Hemmer introduced the so-called Mannheimer Hours 1780, i.e. a reading of the measuring instruments at 7 a.m., 2 and 9 p.m.  mean local time (MOZ), which are still used in meteorology today. Mean values were formed for the daily mean temperature, the measured value from 9 p.m. being taken twice in order to avoid night readings. In addition, phenological and nosological observations should be added.

The instruments for the first international weather network were two thermometers, a barometer, a hygrometer and a declination needle; these instruments were manufactured, calibrated and adjusted by Hemmer in Mannheim. There were also instruments that you could easily make yourself, for which he gave instructions: Electrometer (measurement of air electricity), anemometer (an anemometer for wind speed, wind direction), rain gauge and evaporation gauge.

The international network had a total of 39 stations, mostly connected to observatories, Jesuit colleges or monasteries, including 14 stations in "German states", 2 in the Habsburg Empire, 2 in Switzerland, 4 in Italy, 3 in France, 4 in BENELUX, 4 in Scandinavia, 3 in Russia, 1 in Greenland, 2 in New England, Mass., United States.



State of preservation 
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    Date: 2021-08-05 20:26:34
    Author(s): Gudrun Wolfschmidt

The old Mannheim Observatory in its new splendor a

Fig. 18. The old Mannheim Observatory in its new splendor after the restoration (2017) (Photo: Kai Budde)

The old observatory in its new splendor after the renovation work was completed in 2017 (Photo: Kai Budde)

The Tower of the observatory is well preserved, restored from 1905 to 1906 and in 1958 after WWII. In a recent restoration (2013--2016), for Mayer’s 300th birthday, the historic dome was placed back on the octagonal substructure of the tower.

Restored staircase of Mannheim Observatory (2016)

Fig. 19. Restored staircase of Mannheim Observatory (2016) (Photo: Kai Budde)

The Mannheim instruments were donated in 1983 to the State Museum for Technology and Work, today Technoseum, in Mannheim, where some of them are part of the permanent exhibition.
The large telescope of Mannheim Observatory from 1859 was given to the city of Karlsruhe in 1957 for the construction of the Volkssternwarte Karlsruhe, another instrument to the Volkssternwarte Heppenheim.

The valuable library of Mannheim Observatory, the oldest book dates from 1476, were transferred to the manuscript department of the Heidelberg University Library.


Comparison with related/similar sites 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
    Entity: 197
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    Date: 2021-08-05 20:29:34
    Author(s): Gudrun Wolfschmidt

Mannheim Observatory (Wikipedia, Rudolf Stricker)

Fig. 20. Mannheim Observatory (Wikipedia, Rudolf Stricker)

Mannheim is a Tower Observatory like there exist in 18th century many Baroque Tower Observatories (Italy "Specola" Bologna, Padova), Clementinum Prague, Kassel, and the large Tower Observatories Kremsmünster and Breslau


Threats or potential threats 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
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    Date: 2021-05-29 17:00:40
    Author(s): Gudrun Wolfschmidt

no threats


Present use 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
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    Date: 2021-08-05 20:31:11
    Author(s): Gudrun Wolfschmidt

After WWI, Professor Heinickel installed a Camera Obscura on the platform of the observatory, in order to provide for visitors to enjoy a panoramic view of Mannheim.

Inside the Tower of Mannheim Observatory, an artist’s workshop was created, these studio rooms were used by many artists since around 1930s.


Astronomical relevance today 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
    Entity: 197
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    Date: 2021-08-05 20:31:42
    Author(s): Gudrun Wolfschmidt

no longer used for astronomy since 1880.

On the upper platform of the building, there is still the arc measurement pillar that serves as the zero point for the Baden surveying system.



Bibliography (books and published articles) 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
    Entity: 197
    Subentity: 1
    Version: 4
    Status: PUB
    Date: 2021-08-05 20:34:45
    Author(s): Gudrun Wolfschmidt

  • Budde, Kai: Wirtschaft, Wissenschaft und Technik im Zeitalter der Aufklärung. Mannheim: Landesmuseum für Technik und Arbeit 1993.
  • Budde, Kai: Sternwarte Mannheim. Die Geschichte der Mannheimer Sternwarte 1772-1880. Ubstadt-Weiher; verlag regionalkultur (Technik + Arbeit 12. Schriften des Landesmuseums für Technik und Arbeit in Mannheim) 2006.
  • Budde, Kai: Das große Buch zur Mannheimer Sternwarte. Mannheim: Waldkirch-Verlag 2020.
  • Budde, Kai: Personal communication concerning text and images, 2021.

  • Christensen, K.: Carl Friedrich Gauß und die Erforschung des Erdmagnetismus. .... 2011.

  • Fuchs, Carl Ludwig: Schloss Schwetzingen. Schwetzingen: Schimper-Verlag 1991

  • Günther, Siegmund: Mayer, Christian. In: Allgemeine Deutsche Biographie (ADB). Band 21. Leipzig: Duncker & Humblot 1885, S. 89-91.

  • Kistner, Adolf: Die Pflege der Naturwissenschaften in Mannheim zur Zeit Karl Theodors. Mannheim: Selbstverlag des Mannheimer Altertumsvereins 1930.

  • Moutchnik, Alexander: Forschung und Lehre in der zweiten Hälfte des 18. Jahrhunderts. Der Naturwissenschaftler und Universitätsprofessor Christian Mayer SJ (1719--1783). Augsburg: Erwin Rauner Verlag (Algorismus, Studien zur Geschichte der Mathematik und der Naturwissenschaften; Bd. 54) 2006.

  • Reichert, Uwe: Hundert Jahre Landessternwarte Heidelberg-Königstuhl. In: Sterne und Weltraum ... (1998), Heft 12, S. 1036-1044.

  • Repsold, Johann Adolf: Zur Geschichte der Astronomischen Messwerkzeuge, Band 1: Von Purbach bis Reichenbach, 1450 bis 1830. Leipzig: Engelmann 1907.

  • Schmeidler, Felix: Mayer, Christian. In: Neue Deutsche Biographie (NDB). Band 16, Duncker & Humblot, Berlin 1990, S. 536 f.

  • Umland, Regina: Heinrich Christian Schumacher (1780-1850) In: Wolfschmidt, Gudrun (Hg.): Astronomie im Ostseeraum -- Astronomy in the Baltic. Hamburg: tredition (Nuncius Hamburgensis; Band 38) 2018, S. 300--321.

  • Wolfschmidt, Gudrun: Venustransit-Expeditionen - Instrumente, Beobachtung, Auswertung. In: Wolfschmidt, Gudrun (Hg.): Sonne, Mond und Sterne - Meilensteine der Astronomiegeschichte. Zum 100jährigen Jubiläum der Hamburger Sternwarte in Bergedorf. Hamburg: tredition (Nuncius Hamburgensis; Band 29) 2013, S. 290--317.

  • Wolfschmidt, Gudrun (Hg.): Astronomie im Ostseeraum -- Astronomy in the Baltic. Proceedings der Tagung des Arbeitskreises Astronomiegeschichte in der Astronomischen Gesellschaft in Kiel 2015. Hamburg: tredition (Nuncius Hamburgensis -- Beiträge zur Geschichte der Naturwissenschaften; Band 38) 2018.

  • Wolfschmidt, Gudrun: Internationalität in der astronomischen Forschung vom 17. bis zum 21. Jahrhundert. In: Wolfschmidt, Gudrun (Hg.): Internationalität in der astronomischen Forschung (18. bis 21. Jahrhundert). Internationality in the Astronomical Research (18th to 21st Century). Proceedings der Tagung des Arbeitskreises Astronomiegeschichte in der Astronomischen Gesellschaft in Wien 2018. Hamburg: tredition (Nuncius Hamburgensis; Band 49) 2020, S. 22--115, hier 1.2.2 Societas Meteorologica Palatina (1780 bis 1795) -- Meteorologie, S. 31--35, Magnetischer Verein Göttingen (1836--1841), S. 35--39.

    Wolfschmidt, Gudrun: Cultural Heritage and Architecture of Baroque Observatories. In: From Alexandria to Al-Iskandariya, astronomy and culture in the ancient Mediterranean and beyond. European Society for Astronomy in Culture - Société Européenne pour l’astronomie dans la culture (SEAC), Proceedings of the 17th Annual SEAC Meeting 2009 in Alexandria, Egypt. Ed. by Michael Rappenglück et al. Oxford, England: Archaeopress / British Archaeological Reports (B.A.R.) 2021.


Links to external sites 
  • InfoTheme: Astronomy from the Renaissance to the mid-twentieth century
    Entity: 197
    Subentity: 1
    Version: 3
    Status: PUB
    Date: 2021-05-29 17:33:35
    Author(s): Gudrun Wolfschmidt



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