Peuerbach’s renowned work on the theory of planets – actually a lecture script
by his student Regiomontan – was written in 1460, one year before his death.
The Theoricae novae planetarum are based on the familiar teachings of
Ptolemy, Al-Battani, Al-Farghani and caliph Al-Mammun’s astronomer, whose
name is unknown. The word “novae” in the title is not meant to refer to a
completely new theory but only to emphasize that this work is a compilation of
the latest contemporary scientific knowledge.
Peuerbach’s work gradually replaced leading textbooks of the time such as
Sphaera materialis by Johannes de Sacrobosco. By 1653 the Theoricae novae
was printed no less than 56 times, which made it to one of the most significant
scientific books in the Renaissance. Even Kepler and Kopernikus founded
their theories on this work.
The invention of the incunabulum is attributed to Peuerbach’s pupil Johannes
Müller von Königsberg (Regiomontanus). After he had left the court of King
Matthias Corvinus of Hungary in 1471, Regiomontanus settled in Nürnberg,
where he was granted the right of establishment until November 29, 1471 (at
first until Christmas 1472 only). According to newer sources Regiomonatnus’
printing office was located in the Karthäusergasse (in the vicinity of today’s
German National Museum). Around 1474 he published an ambitious
publication catalogue entitled “Hec opera fient in oppido Nuremberga
Germanie ductu Ioannis de Monteregio”. As the first two entries of the long list
were mentioned “Theorice nov[a]e planetarum Georgii Purbachii astronomi
celebratissimi: cum figurationibus opportunis” and “Marci Manlii astronomica”.
Added to both titles was the following important note: “Hec duo explicita sunt”,
declaring that these two books had already been printed.
According to Aschbach’s “Geschichte der Universität Wien im ersten
Jahrhunderte ihres Bestehens” (Vienna 1865) Regiomontanus was the first
scholar who was aware of the importance of book printing for science and who
turned it to good account in the fields of mathematics and astronomy.
It goes without saying that publishing Peuerbach’s major works (some
unfinished) played a central role in this respect.
02. Regiomontanus, Kalendarium, Venice 1476
Regiomontanus’ Calendar – in our collection as a reprint ordered by Erhard
Ratdolt in 1476 – first appeared in 1474 and exceeded by far the calendrical
calculation of Johannes von Gmunden. Regiomontanus not only determined
the time of the full and new moon, but also, according to the knowledge of the
time, the phases of the moon together with the solar and lunar eclipse.
At the end of this work he showed that by taking into account the phases of the moon
and the spring equinox (Dies paschalis iuxta decreta patrum) the dates for
Easter Sunday differed between 1477 and 1532 in no fewer than 30 cases by
one, four and even five weeks as compared to those dates determined by the
principles of the ecclesiastical Easter calculation according to Dionysus (Dies
paschalis iuxta usum ecclesiae), a method which had been laid down at the
council of Niccaea (325). Mainly due to his well-founded criticism of the
method for the Easter calculation, which even back then was almost a
thousand years old, Pope Sixtus IV summoned Regiomontanus to Rome for
consultations on the long and unsuccessfully discussed calendar reform in
1475 (in the end this reform came into effect in 1582 only). Regiomontanus
died in the mid-summer of 1476 in Rome.
The key passage to the Easter calculation is found in our copy on sheet 29-30,
starting (sheet 29v) with the words: „Hic calendarii nostri clauderii nostri
clauderemus usum, nisi quorundam de celebritate paschali dubitatio
succureret […]“.In the following Regiomontanus explains, that the fact that the
spring equinox was not determined in the pre-Gregorian calendar led to very
early Easter dates (e.g. 1484: March 14), while the official determination of the
time – assuming a cyclic recurrence of the Easter date – led to very late Easter
dates (in the same year 1484: April 18 – 35 days later than with the correct
calculation). It was only with the introduction of the Gregorian Calendar that
the Roman Catholic Church took Regiomontan’s legitimate objections into
03. Regiomontanus: Epitoma in Almagestum Ptolemaei, Venice 1496
Regiomontanus’ publication program from 1474 (Hec opera fient in oppido
Nuremberga Germaniae ductu Ioannis de Monteregio) contains as fourth entry the
Magna compositio Ptolemei: quam vulgo vocant Almaeistum [sic] nova traductione.
The Epitoma in Almagestum Ptolemaei is not only a translation of the Ptolemaic
Almagest, but also a commented and improved (as well as partially shortened) Latin
edition. Georg von Peuerbach who initiated this publication-project was never to
finish it. Approaching death in the spring of 1461 he asked his student Regiomontan
to complete the work, ordered by Kardinal Bessarion. The books 1-6 are mainly
written by Peuerbach (c.f. Zinner), whereas the books 7-13 are written by
Regiomontanus. In book number seven Regiomontan made a significant remark on
the precession (“…when appointing an unknown movement to the stars, it is
necessary to persistently observe them…”). In the ninth book there is among others
an interesting thought about the inability to observe Venus transits due to a supposed
relation between the apparent diameter of the Sun and Venus of 10:1 (however,
under this assumption, the only impossible thing to observe is the decrease in the
sun’s brightness of about 1% during a transit, which was simply due to the then
available equipment!). Furthermore it is important to note, that Peuerbach and
Regiomonatnus considerably improved those parts of the Almagest which refer to the
At the end of proposition XXII of the fifth book it says: “Sed mirum est […] in
quadratura luna in opposito augis epicycli existente non tanta appareat: cum tamen
si integra luceret: quadrupla opportet apparere ad magnitudinem suam, quae apparet
in oppositione, cum fueret in auge epicypli.” With this, Peuerbach highlights a weak
spot in the Ptolemaic theory (by the way this was already criticised by H. v.
Langenstein). According to the Ptolemaic theory the area the moon holds on the sky
should change by a factor of four during one revolution (its angular diameter by a
factor of two respectively).
Among the readers of the Epitoma in Almagestum Ptolemaei were famous
astronomers such as Kopernikus or Galileo. Here they could find their criticism of the
geocentric theory foreshadowed.
04. Nicephorus Blemmyda: Nicephori Logica, Venice 1498
05. Pseudo Proclus Diadochus: Procli Diadochi Sphaera, Venice 1499
06. Heinrich von Langenstein, Secreta Sacerdotum, Strasbourg 1505
Although Heinrich von Langenstein was very famous in the late Middle Ages, he is
hardly known today. Therefore a short summary of his life and works is given in the
Heinrich Heinbuche von Langenstein (also known as Heinrich von Hessen or
Henricus de Hassia), who received his degrees as magister atrium and magister
theologiae in Paris, was offered a chair of theology in Vienna in 1383, where he
taught until his death in 1397.
In 1383, when Langenstein came from Paris to Vienna, the theological faculty had
just been added to the university. Its equipment was still very poor and J. Aschbach
writes in his previously mentioned “Geschichte der Universität Wien im ersten
Jahrhunderte ihres Bestehens” (p. 378f.): „There wasn’t a proper university building,
there wasn’t any space to store the books, there wasn’t a church connected to the
university. The localities used by the university were in such a deplorable state that
they didn’t even provide protection from the wind and rain. They also weren’t roomy
enough and their location in the middle of the city’s traffic and noise was disturbing
and distracting from the studies. The teachers didn’t receive a regular income and the
discipline of the scholars couldn’t be maintained, as long as the principal was not
entitled to the complete jurisdiction […].” By pointing out these unbearable
circumstances and during his time as principal from 1393 to 1394 Langenstein
helped to improve the situation (also including the equipment of the building). In
addition, the careful education of the students of natural sciences was of utmost
importance to him; the number of lectures as well as the requirements at exams were
Langestein produced a great number of works – most of them only in the form of
manuscripts – in natural, theological, political and economic science in Latin. Besides
there are also some scripts in German as well as some scripts dealing with
astronomy. His Quaestio de cometa is written on the occasion of the appearance of
the comet in 1368, in which he denies the influence of stars and in particular of
comets on human behavior (cf. Hubert Przechlewski, Heinrich von Langensteins
Quaestio de cometa und der astrologische Irrwahn seiner Zeit, diss., Breslau 1924).
In another work he referred to the discrepancy between the planetary theory of
Ptolemy and the astronomical reality. (According to the teachings of Ptolemy the
apparent angular diameter of the moon should at certain positions of its course
change by a factor of two. At that time, this reference to the obvious error of the
Ptolemaic theory was only noticed by a few scholars [i.e. Regiomontanus])
The present work, Secreta Sacerdotum, is one of Langenstein’s theological works, to
which also belong among others: De verbo incarnato; De contemptu mundi (newly
published in: Zeitschr. f. Kath. Theol. 29, 406-412); De missa; De confessione.
07. Claudius Ptolemaeus, Almagestum, Venice 1515
08. Jacques Lefèvre d’Etaples, Introductorium astronomicum, Paris 1517
09. Petrus Apian, Astronomicum caesareum, Ingolstadt 1540
10. Johannes Kepler, De Stella nova …, Prague 1606
11. Johannes Hevelius, Mercurius in Sole visus Gedani,…, Danzig 1662
12. John Flamsteed, Atlas Coelestisi, London 1753
13. Maximilian Hell, Observatio transitus Veneris antediscum Solis die 3 Junii anno 1769, Kopenhagen 1770
14. Maximilian Hell, Beobachtung des Durchganges der Venus durch die Sonnenscheibe, Breslau/Hirschberg 1793
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