Astronomical Observations

The second part of the first volume of Danubius Pannonico-Mysicus relates to the presentation of the astronomical observations that were carried out by Marsili and Johann Christoph Müller (1673-1721) during 1696 and 1697. These observations were essential to calculate longitude and latitude, which was necessary to determine the geographic position and distances between places in order to complete the drawing of the maps. The maps that Marsili and Müller produced from their astronomical observations were, despite some distortions due to the relatively low number of measurements taken rather than imprecisions in their recording, more accurate than previous maps and corrected errors in the course of the Danube.[1]

Luigi Ferdinando Marsili, Danubius Pannonico-Mysicus: Observationibus Geographicis, Astronomicis, Hydrographicis, Historicis, Physicis (The Hague & Amsterdam, 1726), i, p. 43. Observations of Jupiter and its moons.

Marsili was in correspondence with the noted mathematician and astronomer Giovanni Domenico Cassini (1625-1712) who advised him to acquire reliable instruments and, along with Georg Christoph Eimmart (1638-1705), instructed him on how to conduct astronomical observations.[2] Cassini was appointed principal chair of astronomy at the University of Bologna in 1650 and he published an ephemeris containing tables on the movements of Jupiter’s satellites that could be used to calculate longitude entitled Ephemerides Bononienses mediceorvm sydervm (Bologna, 1668). The acclaim that this publication brought him led to King Louis XIV (1638-1715) inviting him to Paris in 1669 where he became the director of the Paris Observatory upon its completion in 1671.[3]

Marsili commissioned scientific instruments including a portable brass quadrant and a sextant from Eimmart, which were used together with compasses, a telescope, a precise clock and astronomical charts to take observations.[4] Eimmart sent his pupil Müller from Nuremberg to Vienna at the end of March 1696 with some of the instruments where Marsili and Müller carried out the first of their observations together. Marsili then sent Müller on a three-month assignment from June to September to particular locations in Hungary and Serbia, where he stayed for several days at a time depending on the suitability of the weather conditions, to carry out different sets of observations.[5]

The locations and dates where Müller observed Jupiter and its satellites in order to calculate longitude measurements are tabulated in four charts in Danubius Pannonico-Mysicus with illustrations of the observations depicted in a column on the right-hand side of each chart. He carried out these observations at Vienna, Buda, a village called Gobinum six and a half kilometres south of Buda, on an island an hour and a half’s walking distance south of Tolna and at Baja in Hungary, the confluence of the river Drava and the Danube, Szeged in Hungary, Senta in Serbia, on a bridge crossing a swamp near Udvar in Hungary, and a military camp outside Titel in Serbia near the confluence of the river Tisza and the Danube.[6]

Müller also used compasses to measure terrestrial magnetic declination, which is the difference between magnetic and geographic north, to determine longitude. These readings were published in the Prodromus printed in Nuremberg in 1700, but were omitted from the Danubius Pannonico-Mysicus.[7] Marsili and Müller both used compasses to record the correct courses and direction in the bends of the Danube and its tributaries.[8]

The lunar observations recording alterations in the phases of the moon are reproduced in sixteen illustrations on eight plates in Danubius Pannonico-Mysicus, one plate of which is shown above. Maria Clara Eimmart (1676-1707), the daughter of Georg Christoph Eimmart, drew the illustrations from drawings Müller recorded in his journal, which were then engraved by her father.[9] Astronomers believed at the time that accurate observations of the moon phases could be used to calculate longitude, but the method was later abandoned because of the complexities involved in recording measurements precisely in order to limit the number of errors to an acceptable amount.[10] Müller’s journal, which records the itinerary of his travels and the observations he made, along with the prevailing conditions at the time, is preserved among the Marsili manuscripts in the Biblioteca Universitaria di Bologna.[11]

Müller measured the culmination points of fixed stars to determine polar altitudes, which are equivalent to geographic latitude. Müller took the measurements at the same locations that he observed Jupiter and its satellites at Vienna, Buda, Baja, the mouth of the Drava, Szeged, and Titel, but he also recorded observations at Szolnok, Eger, and Buda again in Hungary on his journey back to Vienna.[12] The measurements recorded at the eight locations and the dates that they were taken are tabulated in charts across seven pages in Danubius Pannonico-Mysicus, one page of which is shown in the image above. He also measured the altitude of the midday sun as it transited the meridian at all of these locations as an additional method of calculating latitude.[13]

The above image depicts Mercury passing in front of the sun, which was observed and recorded by Marsili and Müller in Vienna on the morning of 3 November 1697.

TEXT: Mr Antoine Mac Gaoithín, Library Assistant at the Edward Worth Library.

SOURCES

Bartha, Lajos, ‘The determination of early longitudes and base meridians in Hungary’, Vistas in Astronomy, 28 (1985), 41-48.

Deák, Antal András (ed.), A Duna Fölfedezése. Luigi Ferdinando Marsigli, Danubius Pannonico-Mysicus. Tomus I, A Duna Magyarországi és Szerbiai Szakasza = The Discovery of the Danube. Luigi Ferdinando Marsigli, Danubius Pannonico-Mysicus. Volume I, The Hungarian and Serbian Section of the Danube (Budapest, 2004).

Deák, Antal András, Maps from under the shadow of the crescent moon = Térképek a félhold árnyékából = Carte geografiche dall’ombra della mezzaluna = Landkarten aus dem Schatten des Halbmondes (Esztergom, Hungary, 2006).

Deák, Antal András, ‘Marsigli, Luigi Ferdinando’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), pp 920-922.

Deák, Antal András, ‘Müller, Johann Christoph’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), pp 1019-1020.

Pelletier, Monique, ‘Cassini (I), Jean-Dominique’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), pp 251-254.

Sandman, Alison, ‘Longitude and Latitude’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), pp 735-750.

Stoye, John, Marsigli’s Europe, 1680-1730 : the life and times of Luigi Ferdinando Marsigli, soldier and virtuoso (New Haven & London, 1994).

[1] Deák, Antal András (ed.), A Duna Fölfedezése. Luigi Ferdinando Marsigli, Danubius Pannonico-Mysicus. Tomus I, A Duna Magyarországi és Szerbiai Szakasza = The Discovery of the Danube. Luigi Ferdinando Marsigli, Danubius Pannonico-Mysicus. Volume I, The Hungarian and Serbian Section of the Danube (Budapest, 2004), p. 139.

[2] Deák, The Discovery of the Danube, pp 119-120 & 138-139; Stoye, John, Marsigli’s Europe, 1680-1730 : the life and times of Luigi Ferdinando Marsigli, soldier and virtuoso (New Haven & London, 1994), pp 134-135.

[3] Pelletier, Monique, ‘Cassini (I), Jean-Dominique’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), pp 251-252; Sandman, Alison, ‘Longitude and Latitude’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), p. 738.

[4] Deák, The Discovery of the Danube, pp 119-120 & 138-141; Deák, Antal András, ‘Marsigli, Luigi Ferdinando’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), p. 921; Deák, Antal András, ‘Müller, Johann Christoph’, in Matthew H. Edney & Mary Sponberg Pedley (eds), The History of Cartography. Volume 4, Cartography in the European Enlightenment (Chicago & London, 2019), p. 1019; Stoye, Marsigli’s Europe, 1680-1730, p. 135.

[5] Deák, The Discovery of the Danube, pp 141-143; Stoye, Marsigli’s Europe, 1680-1730, pp 135-137.

[6] Deák, The Discovery of the Danube, p. 142; Stoye, Marsigli’s Europe, 1680-1730, pp 135-137.

[7] Deák, The Discovery of the Danube, p. 143; Sandman, ‘Longitude and Latitude’, p. 743; Stoye, Marsigli’s Europe, 1680-1730, p. 136.

[8] Deák, ‘Marsigli, Luigi Ferdinando’, p. 921; Deák, ‘Müller, Johann Christoph’, p. 1019.

[9] Deák, The Discovery of the Danube, p. 142; Deák, ‘Müller, Johann Christoph’, p. 1019.

[10] Deák, The Discovery of the Danube, pp 142-143.

[11] Deák, The Discovery of the Danube, pp 141-142; Stoye, Marsigli’s Europe, 1680-1730, p. 135.

[12] Deák, The Discovery of the Danube, pp 141-142; Stoye, Marsigli’s Europe, 1680-1730, pp 135-137.

[13] Deák, The Discovery of the Danube, p. 142; Stoye, Marsigli’s Europe, 1680-1730, pp 135-137.

Astronomical Observations

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