Explanation of the digital exhibition '400 years of the telescope'
This sub-collection containing digitized celestial maps commemorates the invention of the telescope four hundred years ago. The new instrument caused a revolution in astronomy, resulting in the downfall of all old views about the central place of the earth in the universe and about the nature and structure of the celestial bodies which were then known. Together with the invention and development of the microscope, the air pump and the pendulum clock, the telescope was responsible for a series of new discoveries and insights which lay at the basis of the scientific revolution which took place in Europe in the seventeenth century. Because of the importance of this "Dutch" invention and the revolution it caused in astronomy, 2008 was declared the Year of the Telescope and 2009 the Year of Astronomy.
On this website nearly hundred digitized celestial maps from the collection of the Utrecht University Library illustrate how cartographers and astronomers in the past four centuries have shown laymen and scientists their new insights, gained with the help of the telescope, about the sun, the moon, the planets and the starry sky.
1608, Middelburg and the invention of the telescope
Until the beginning of the seventeenth century, the human eye was the only means of observation and this meant precision was limited. This changed when a rumour spread throughout Europe in the last months of 1608 that a spectacle maker from the city of Middelburg had invented a miraculous instrument. This instrument not only made it possible to show faraway objects but also to make it look as if they were near by. To astronomers as well, this instrument, soon to be called the telescope, could be of use because now they were able to see numerous faint stars as well which up to then had been invisible to the naked eye.
The first scientist to realize the astronomical usefulness of this new instrument was the Italian Galileo Galilei (1564-1642). In 1609 he built his own telescope which he used to scan the sky. In the course of only a few months time he discovered "seas" and mountains on the moon, four hitherto unknown moons near the planet Jupiter, and that the light shining from the Milky Way was caused by countless weak stars invisible to the naked eye.
After Galileo Galilei had published these discoveries in his Sidereus Nuncius (Starry Messenger) in the spring of 1610, more discoveries were made such as spots on the sun, the phases of Venus and curious phenomena near the planet Saturn. He used these discoveries to support the heliocentric world system advanced by the Polish canon Copernicus (1473-1543). After other scholars such as Johannes Kepler, Pierre Gassendi, Johannes Hevelius and Christiaan Huygens had confirmed Galileo’s discoveries and added their own, it became clear that the ancient geocentric worldview (with its supposed strict separation between the "sublunar" and "celestial" realms) could no longer be maintained.
Until late in the sixteenth century, western astronomers had to depend for the depiction of the fixed stars on the catalogue of stars containing 1,022 stars arranged in 48 constellations, which Claudius Ptolemaeus of Alexandria (second century A.D.) had included in his Almagest. According to the custom of those days, the constellation figures on celestial maps and globes were given a prominent place and depicted with much artistic insight.
Also for celestial cartography, the telescope meant the beginning of a new era. Firstly: more stars were visible, now that the naked eye was not the only means of observation and secondly: also their position in the sky could be recorded with greater precision. As a result, more extensive celestial catalogues and atlases were published describing an increasing number of stars (over 1,600 around the year 1700, over 17,000 around the year 1800 and approximately 325,000 around 1900). Together with the mapping of the southern starry sky (invisible from Europe), this led to the introduction of many new constellations which number had increased to over a hundred around the year 1800.
But also the sun, the moon, planets and comets have been studied in detail during the past four centuries. In particular the moon was a popular object of observation and numerous maps of its surface were published.
Remarkable celestial phenomena such as solar and lunar eclipses, transits of planets in front of the solar disc and the predicted return of periodic comets led to the printing of special maps and pamphlets in which these celestial phenomena and their designated times were predicted. They were very popular, not only with scholars but also with the lay public.
Selection of the digitized celestial maps
It may be clear that only a small part of the enormous collection of celestial atlases, maps and prints in the Utrecht University Library can be shown on this website. Besides the well-known maps from the famous celestial atlases by Johannes Bayer (1603), Andreas Cellarius (1660), Johannes Hevelius (1690), John Flamsteed (1729), Johann Gabriel Doppelmayer (1742) and Johann Elert Bode (1801), in particular many less well-known and rare copies were selected. Also included are many celestial maps of Dutch origin, which are largely unknown in the literature on celestial cartography.
The selection is mainly based on early printed material which for some time has been part of the library collection: the extensive map collection of the Utrecht mathematician, physicist and astronomer Gerrit Moll (1785-1838) and the collection of celestial atlases and maps of the Astronomical Institute which has recently been added to the map collection as the ‘Sonnenborgh collection’. From the early printed works various titles were selected from the extensive collection of astronomy books by Jacob Maurits Carel baron of Utenhove van Heemstede (1773-1836) and which his widow donated to the Utrecht University Library in 1837.
As far as possible, the sub-collection 400 years of the telescope is arranged in chronological order. Each map is provided with an extensive description, including title, author, publisher, technique, measurements and of course bibliographical data. In addition, each map comes with an extensive scientific explanation, illustrating the place of the map in the development of celestial cartography. If necessary, extensive references to relevant literature are included. The descriptions and scientific explanations were written by Dr R.H. van Gent, astronomer of Utrecht University. The photography and digitization of the maps was primarily the work of Adriaan van Dam. The realization of this sub-collection of digitized maps was made possible by a grant from the K.F Hein Fund as part of the Utrecht University Fund.