Tabulae directionum profectionumque
| Author | Regiomontanus, Johannes |
|---|---|
| Full title | Tabulae directionum profectionumque famosissimi viri magistri Joannis Germani de Regiomonte in nativitatibus multum utiles |
| Year | 1490 |
| Place | Augsburg |
| Publisher/Printer | Ratdolt |
| Era | 15th century since invention of printing |
| Form/Genre | Tables and charts |
| Discipline/Content | Mathematics, Astronomy/Astrology/Cosmography |
| Digital copies | |
| Original | Tabulae directionum profectionumque (ULB Darmstadt) |
| Digital sourcebook | 928891 |
| Description | This is one of the most influential collections of astronomical tables to be printed during the Renaissance. Composed as early as 1467, but published only posthumously in 1490 under the supervision of the astronomer Johann Engel, as detailed on the last page, the Tables of the Celestial Movements (for the exact meaning of the two technical terms in the title see Lexicon mathematicum, astronomicum, geometricum, pp. 142 and 388) was reprinted, sometimes with additions, until 1606.
The letter of dedication to Johann Beckenschlager, the archbishop of Esztergom, who had commissioned the work, provides a short overview of the history of astronomical tables, starting from Ptolemy's Almagest, describes the difficulties involved in their compilation and emphasizes their utility for astrologers and others. The work proper starts with the discussion of 31 probleumata (sic), which explain the use of the following tables in order to answer various astronomical and astrological questions. The tables proper fill some 230 pages. Some of them are general tables of chords (the predecessors of trigonometric functions used throughout European antiquity). Regiomontanus chooses 100,000 as radius (sinus totus) of the defining circles in order to avoid fractions in the tables of trigonometric functions. The so-called tabula fecunda ("fruitful table") on fol. 30r gives the tangent (whose value is called simply numerus) for each degree from 0° to 90°. Most tables, however, indicate the positions of the zodiacal signs in degrees and minutes for a given time and place. This reflects an important purpose of the collection, namely the computation of astrological houses and their borders for the generation of horoscopes, an aspect highlighted already in the title (in nativitatibus multum utiles). As an average page contains some 200 figures, the calculations involved must have been a Herculean task. The terminology, abbreviations and symbols used are technical and hard to understand for the non-expert in early modern astronomy. On the last page, the printer has proudly placed his coat of arms along with a short epigram. |
| References | Zinner 1968, 147-151 Merzbach; Boyer 2011, 248 Complete Dictionary of Scientific Biography 2008, vol. 11, 350 |
| Cited in | |
| How to cite this entry | Regiomontanus, Johannes: Tabulae directionum profectionumque, in: Noscemus Wiki, URL: http://wiki.uibk.ac.at/noscemus/Tabulae_directionum_profectionumque (last revision: 22.02.2022). |
