Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae. Willebrord Snellius, Tycho Brahe, Landgrave of Hesse-Kassel Wilhelm IV, Jost, Bürgi, Christoph Rothmann, Johannes Kepler, 1532 –1592.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.
Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.

Coeli & siderum in eo errantium observationes Hassiacae, principis Wilhelmi Hassiae Lantgravii auspiciis quondam institutae. Et spicilegium biennale ex observationibus Bohemicis V.N. Tychonis Brahe. Nunc primum publicante Willebrordo Snellio. R.F. Quibus accesserunt Ioannis Regiomontani & Bernardi Walteri Observationes Noribergicae.

Leiden: Joost van Colster, 1618.

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Quarto: 18.8 x 14.5 cm. Two parts in one volume, as issued: [12], 116 p.; 68 ff. Collation: (*)4, (**)2, a-o4, p2; A-R4

FIRST EDITION.

Bound in contemporary vellum (lightly soiled, label chipped). Contents with light, variable browning due to paper quality but on the whole still quite fresh. Fore-edge of title slightly chipped, damp-stain to lower, inner corner of last 4 leaves. With 11 woodcut diagrams in the text, including two of instruments. Provenance: Armorial bookplate of the Italian intellectual Francesco Vargas Macciucca (1699-1785). On the front paste-down are Vargas Macciucca’s “laws” for borrowing books from his library. (See transcription at foot of this description.).

An important compilation of astronomical data and treatises, many printed here for the first time, edited by the Dutch mathematician and astronomer Willebrord Snellius, professor of mathematics at Leiden. Snellius achieved lasting fame for his development of the optical refraction law that still bears his name. Snellius was well-suited to the task of publishing this volume, having worked as Tycho Brahe’s assistant at Prague from 1599 until the Dane’s death in 1601 (where he worked alongside Kepler), having visited the famous observatory at Kassel, and having published numerous mathematical works.

The book contains the first printing of data from the observatory of the Landgrave Wilhelm IV of Hesse-Kassel (1532 –1592). Wilhelm’s observatory, which predates that of Tycho at Hven by roughly twenty years, has been called the first modern European observatory, though the appropriateness of this terminology has been disputed. Although much more modest than Tycho’s observatory, the Landgrave’s fixed observational platform was progressively outfitted with refined instruments, some built by Wilhelm’s resident instrument maker Jost Bürgi (1552-1632) and operated by Bürgi, Wilhelm and the astronomer Christoph Rothmann (1560-1600), who collected data over a period of thirty years.

In Snellius’ book, the data from the observatory at Kassel comprise observations of the sun from 1561-1582 and of the planets Venus, Mars, Jupiter, and Saturn from 1590-1597, the latter made with the sextant manufactured by Bürgi, who also made a sextant for Tycho. Snellius copied this data from the observatory catalogues during his visit to Kassel in the summer of 1603.

The book also includes the first printing of observations made by Tycho Brahe from 1599 to 1601 (while Snell worked as his assistant in Prague) and the eye-witness account (p. 83-4) of Tycho’s final illness and death by Johannes Kepler, who wrote his account in Tycho’s observation book as a colophon, adding that with Tycho’s death, the recording of observations had come to an end after thirty-eight years. Snell might also have been present at Tycho’s death.

Snellius’ own contribution is a “lengthy piece about the technical difficulties connected to the determinations of parallax and refraction. He based his considerations on a critical assessment of many observations done by different astronomers from Eratosthenes to Copernicus and Brahe, and made calculations involving spherical trigonometry.”(De Wreede, p. 150) This was only three years before Snellius’ discovery of the law of refraction that bears his name.

In the second part of the book are previously-published observations made by Georg von Peuerbach (1423-1461) and Johannes Regiomontanus (1436-1476) in the 1460s, and by Regiomontanus and his collaborator Bernhard Walther (1430-1504) at Nuremberg from 1471 to 1504. Also included are Regiomontanus’ “Sixteen Problems on the Magnitude, Longitude and True Position of Comets”, and Johann Schöner’s (1477-1547) descriptions of two instruments: the “Ptolemaic rule” (for measuring terrestrial and astronomical distances) and the cross-staff (“radius astronomicus”) used by Regiomontanus (and described by him in Problem XII) and by Walther. Finally, there is an excerpt from Kepler’s “Paralipomena ad Vitellonem” and a short text in which Snellius corrects an error made by Schöner.

The title of Snellius’ book reads, ‘Hessian Observations of the heaven and the heavenly bodies that wander upon it, which have once been begun under the command of the most distinguished Prince William Landgrave of Hesse’. It was dedicated to Wilhelm IV’s son and successor, the Landgrave Maurice.

In the dedication, “Snellius implied that he would be a good candidate to continue the work of William and his collaborators: ‘If something could be done in these fields, I would willingly and with great pleasure offer all my services to Your Highness.’ This could be interpreted as meaning that Snellius would stay in Leiden and fulfill any tasks for Maurice there, but it could also mean that he was applying for the position of court astronomer. The last interpretation is not unlikely, because if Maurice seriously wanted to emulate his father's achievements in astronomy, he could not do that without his own court astronomer… If Snellius' goal was indeed to obtain a job from Maurice, it also becomes easier to understand why he presented his edition of the Kassel observations as just a ‘spicilegium’, a ‘pile of leftovers'. It was a topos of modesty, but it also implied that the work had not been finished, that much more work had to be done, that old observations had to be edited and new ones carried out, and Snellius was the right person to do all that….

“We cannot determine whether Snellius planned the ‘Observationes Hassiacae’ mainly as an advertisement campaign for himself, for the accomplishments of observational astronomy of the past one and a half century, or just as a useful compendium of knowledge, yet we do know that he had some success with his readers: Kepler used the book, and Maurice of Hesse gave Snellius a new assignment (in 1619, Maurice asked Snellius for the observation and explanation of several aspects of the comet that had appeared at the end of the previous year.) Daniel Mögling described Snellius’ book in a letter to Wilhelm Schickard of 1631 and he sent an excerpt of the book a year later. Later in 1632, Pierre Gassendi asked François Luillier on behalf of Schickard first to send Schickard a copy of the ‘Observationes Hassiacae’ and then to ask Ismaël Boulliau to make an excerpt of the observations of Mercurius. Boulliau did as requested, sending his notes directly to Schickard.

“Kepler read and used the ‘Observationes Hassiacae’, as can be inferred from several references in his correspondence and in his Tabulae Rudolphinae. He was occupied by the question whether Snellius had possessed the original manuscripts of the observations that he had edited, or just a copy. In 1628 Kepler asked Georgius Brahe, Tycho's son, whether he could try and obtain Tycho's own notebook from 1600 and 1601 from Snellius' widow. He wrongly supposed that someone had brought the book to Leiden during the international political troubles of 1618. Fearing that part of Tycho's own observations were lost, he wrote that 'it would be a shame that we should then content ourselves with just the excerpts of Snellius and trust his edition'. Kepler's worries were unnecessary: he received the requested volume from Tycho's heirs. It is therefore most likely that Snellius copied the notes while he was in Bohemia and that he was present when Tycho died.”(De Wreede, p. 153 ff.)

Wilhelm IV’s Observatory at Kassel:

The Landgrave Wilhelm IV of Hesse-Kassel has achieved lasting fame for his patronage of Tycho Brahe, whose astronomical observatory on the island of Hven (built ca. 1576-80) was financed by the Landgrave. He is also remembered for his own astronomical observations and the castle observatory from which he and his assistants made them.

“In 1560 Wilhelm ordered the construction of a balcony at his urban castle in Kassel. For the next thirty years the observations were implemented there. Most of the measurements were made by Wilhelm IV and his court mechanic Baldewein. Between 1560 and 1563 many observations took place to determine the latitude of Kassel and the inclination of the ecliptic. In the same period the first stellar positions were measured and catalogued… As for the instrumental equipment in the first period of observation, a wooden quadrant and the torquetum were the only instruments used in the years before 1568. According to a treatise by Andreas Schöner, the quadrant had a radius of two feet (ca. 54 cm). Unfortunately there are no details known with certainty concerning the torquetum…

“At the beginning of the second period (1567 to 1584) the organizational structure fundamentally changed: Landgrave Philipp died in 1567, and Wilhelm overtook full political responsibility for one of the Hessian states (divided up by Philipp’s inheritance) and so did not have much time to pursue his astronomical inclinations. Therefore, in the period between 1567 and 1584, the common astronomical activities were limited to the measurement of the meridian elevation of the Sun. However, in 1572 the appearance of the nova in Cassiopeia inflamed astronomical enthusiasm in Wilhelm once more. It is said that not even a fire in his castle could take him away from his instruments…

“Wilhelm’s correspondence with important astronomers and princes at this time increased the reputation of Kassel as a centre of astronomy. The appearance of the comet of 1577 strengthened this reputation. Therefore, in 1575 the young Tycho Brahe visited Kassel, as he searched for astronomical patronage. In the following twenty years the relationship between Tycho and Wilhelm became so close that there was a regular correspondence between Kassel and Hven culminating in the exchange of astronomical data as well as improvements of the instruments.

“How can we assess the personnel and instrumental infrastructure of the second period? The fact that Wilhelm no longer had time for regular observations caused him to look elsewhere for expert assistance. In 1576 he tried to attract Johannes Praetorius to Kassel, but Praetorius refused to come. In the years before 1576 Wilhelm had a court astronomer named Johannes Ottonis. Very little is known of this person except that he recorded the inventory of 1573 and died in 1576. The observations of the nova were certainly implemented by Wilhelm, Ottonis and Victorinus Schönfeld, the professor of mathematics in Marburg. Possibly in 1584 Wilhelm appointed Christoph Rothmann to be his court astronomer and Jost Bürgi as court mechanic.

“There are some new instruments recorded in this period. In 1568 Wilhelm ordered two new brass quadrants. One of them, the “small quadrant”, is almost certainly the famous azimuth quadrant, today a highlight of the Astronomisch-Physikalisches Kabinett of the Kassel State Museums. Its metal configuration is unusual: all the larger instruments of the time were wooden, almost always of some sort of water-resistant wood. It is thus certain that the azimuth quadrant had to be removed from the balcony, at least in the winter months, because brass is not at all waterproof…

“The beginning of the third period is not totally clear. For example, it is not known exactly when between 1580 and 1584 Rothmann was appointed as court astronomer. Little is known about these four years. We only know that the regular measurement of solar positions came to an end—maybe with a satisfying value for the obliquity of the ecliptic and the latitude of Kassel—and that Bürgi improved a quadrant. But the real beginning of the golden times of the observatory is marked by the visit of Paul Wittich, a former assistant of Tycho. He reported some crucial instrumental improvements that had been implemented under Tycho, especially the transversal lines on the scales of the instruments, and the construction of a sextant to measure the reciprocal distances of the stars (distantias stellarum inter se). As a consequence, Bürgi built a sextant for one-man-measurement with a transversal graduation. One year later the most important innovation of Bürgi took place: the longitudes of the stars were measured with the help of a clock invented by Bürgi, rather than directly by angular readings. According to Rothmann’s “Liber observationum stellarum fixarum” the watch had a crossbeat escapement and possibly also a remontoir. This enabled the observers to measure the right ascension of the fundamental star Oculus Tauri (i.e., α Tauri) with the help of the difference of the time of culmination between the Sun and the star. The position of the other stars was measured with the help of angular distances. Thanks to the clock the recorded positions of 383 stars in 1587 were much more precise than those of 1567.

“The period between 1584 and 1589 was a time of constant research in Kassel. Rothmann and Bürgi observed the heavens on every clear night. In a letter to Tycho, Wilhelm mentioned three further assistants. One of them was Rothmann’s younger brother Johann. Kassel was now a true centre of astronomy. The comments of many visitors such as Raimarus Ursus and John Dee bear witness to the fame of the observatory and Landgrave Wilhelm. But the relationship between the most important figures, Rothmann and Bürgi, grew worse and worse. In 1590, Rothmann left Kassel via Uraniborg and never came back. The star catalogue remained unpublished because Wilhelm’s health subsequently weakened, and the same occurred to his interests in astronomy.

“The death of Wilhelm five years later brought the astronomical activities in Kassel progressively to an end. Though Bürgi began to record the positions of the planets, his observations and a few of the star positions were published only in Willebrord Snell’s “Observationes Hassiacae” of 1618.

“The period between 1584 and 1589 was the heyday of the Kassel observatory. New instruments were constructed and improvements to the existing equipment made (Fig. 3). Numbers of observatory staff increased significantly. Kassel was a known quantity in the minds of astronomers and natural philosophers across Europe and a site for the active exchange of ideas, the most important of which came from an ongoing exchange with Uraniborg. We may also conclude that the starting point in 1584 came indirectly from Hven with Wittich’s visit.”(Karsten Gaulke, “The First European Observatory Of The Sixteenth Century, As Founded By Landgrave Wilhelm IV Of Hesse-Kassel”: A Serious Historiographic Category Or A Misleading Marketing Device?, in European Collections of Scientific Instruments, 1550-1750, pp. 87-97)

Casper 56; Bierens de Haan 4392; Poggendorff II, 948; Zinner 1857, note. - ADB XXIX, 370 (Rothmann).

The “Laws” for borrowing this book:

The Italian intellectual and lawyer, Francesco Vargas Macciucca (1699-1785), was fervently interested in philosophy (he endured accusations of atheism and Cartesianism), science, and music. Among his many published works are a tract on musical counterpoint and a translation of Ralph Cudworth’s “True Intellectual System of the Universe”. His unusual, printed list of rules for borrowing books form his library, pasted on the front endpaper of this book, reads:

Leges, Volumina ex Bibliotheca nostra commodato accepta, lecturis , Secundum auspicia lata Lictor Lege agito in Legirupionem. Mas vel Foemina fuas, hac tibi lege, Codicis istius usum, non interdicimus. 
I. Hunc ne Mancipium ducito. Liber est : ne igitur notis compugito. 
II. Ne coesim punctimve ferito : hostis non est. 
III. Lineolis, intus, forisve, quaquaversum, ducendis abstineto. 
IV. Folium ne subgito, ne complicato, neve in rugas cogito. 
V. Ad oram conscribillare caveto. 
VI. Atramentum ultra primum exesto ; mori mavult quam foedari. 
VII. Puroe tantum papyri Philuram interserito. 
VIII. Alteri clanculum palamve ne commodato. 
IX. Murem, tineam, blattam, muscam, furunculum absterreto.
X. Ab aqua, oleo, igne, situ, illuvie arceto. 
XI. Eodem utitor, non abutitor. 
XII. Legere, et quaevis excerpere, fas esto. 
XIII. Perlectum, apud te perennare ne sinito. 
XIV. Sartum tectumq., prout tollis, reddito. 
XV. Qui faxis, vel ignotus Amicorum albo adscribitor : qui secus, vel notus eradetor. 
Has sibi, has aliis preescribit leges in re sua, Ordinis Hyeresolimitani Eques Dux Thomas Vargas Macciucca. Quoi placeas annue, quoi minus, quid tibi nostra tactio est? Facesse.
(See "Zeitschrift für Bücherfreunde", first issue, second vol., 1897/98, p. 433).