The treatise on the composition and the use of the astrolabe by Cristannus of Prachatice
Dr Alena Hadravova and Petr Hadrava
The critical edition of treatises on the composition (Quamvis de astrolabii composicione tam modernorum quam veterum dicta habentur pulcherrima ...) and the use (Quia plurimi ob nimiam quandoque accurtacionem ...) of the astrolabe by Magister Cristannus of Prachatice has been prepared as the first step of a long-term project on study of the up to now poorly known medieval astronomical Latin manuscripts and old prints of Czech provenance. Cristannus wrote his treatises in 1407 for his lectures in Prague University. Owing to their didactical qualities, the treatises were spread throughout the Europe in many manuscripts (there are known about 80 mss.) and also in the form of incunabula (Perugia 1477-79 etc.) and old prints. However, Cristannus as a prominent Hussite was a ‘persona non grata’ in Catholic Europe. It explains why his authorship of both treatises was mostly concealed, forgotten and later wrongly attributed either to Robertus Anglicus or Prosdocimus de Beldomandi, despite the fact that the Prague origin is obvious from the texts. A redaction of the Cristannus’ treatises was written by Magister Iohannes of Gmunden in Vienna; an edition of his version is also prepared for comparison.
The treatise on the eclipse instrument by Iohannes Schindel, and links between the Prague and Vienna astronomical schools
Dr Petr Hadrava
This paper deals with the treatise on an eclipse instrument by Iohannes Schindel and with links between Prague and Vienna astronomical schools. Magister Iohannes Andreae dictus Schindel (c. 1375-1458), rector of the Charles University and physician of king Venceslaus IV and emperor Sigismund, is renowned as the astronomer in collaboration with whom the clockmaker Nicolaus of Kada constructed the famous Astronomical Clock of Prague in 1410. According to the testimony of Tycho Brahe, Schindel also performed valuable astronomical observations. Recently, Schindel’s theoretical treatises on the construction and the use of astronomical instruments were identified. A critical edition of his treatise Canones pro eclipsibus Solis et Lune per instrumentum ad hoc factum inveniendis Magistri Iohannis Schindel is now in preparation. Schindel’s eclipse instrument was derived from Wallingford’s albion. All three known manuscripts of Schindel’s treatise are in convolutes together with either Wallingford’s albion or its version enlarged by Iohannes of Gmunden (the edition of the later will be also added for comparison). This example illustrates the connections between Prague and Vienna astronomical schools in both of which Schindel was active.
Saxonian astrolabes made by Ercker, Trechsler, Starck and Pregel in the 16th and 17th Centuries
Dr Peter Plassmeyer
In 1999 the Mathematisch-Physikalischer Salon, Dresden bought an important astrolabe from the Rothschild Collection. This astrolabe signed ‘Thomas Pregel von Nor: fecit Swickau 1629’ is one of the last European instruments of its kind. Without a dorsum and with its own kind of curve on the planisphere, it depends more on those astrolabes we can find as clock-dials than on those from the Regiomontanus- and Arsenius-types. Pregel changed the curves for unequal hours with those for the Italian and Bohemian hours, as we can find it in Franz Ritter’s treatise on an astrolabe, printed in Nuremberg 1613. These curves are also similar to the Nuremberg hours.
Ernst Zinner describes another three astrolabes made in Saxony. The first by Zacharias Ercker dates from 1567 and was made and used in Annaberg. The second was made in 1615 by the most important Saxonian instrument maker, Christoph Trechsler, and today is on display in the National Maritime Museum in Stockholm. It is different from Ercker’s small but complete astrolabe, since it only shows the curves pertinent to horoscopes. Viktor Starck’s astrolabe (1632) was formerly in a private collection in Altenburg (near Leipzig) and nothing is known about this collection today. Zinner gives a brief description which explains an instrument in the Trechsler manner. Starck as well as Pregel were temporary assistants in Trechsler’s workshop.