Astronomy in Salamanca in the Mid-Fifteenth Century: The <i>Tabulae Resolutae</i>

Chabás, José

doi:10.1177/002182869802900209

Cited by 15 publications

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“…Since the lunar diameter is about 0;30°, the distance between the centres of the Moon and Venus has been computed to be about 3! times that amount (see Appendix, [12]). This leads Zacut to dismiss the instructions of John of Ligneres (a similar remark appears in the canons to the 1496 edition of his tables), 29 but he still has to deal with the problem of reconciling theory and observation, an issue that only rarely arose in the medieval astronomical literature.…”

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“…For his computations Zacut used some version of the Alfonsine Tables, probably the Tabulae resolutae brought to Salamanca by Nicholas Polonius, c. 1460. 12 Recomputing with the parameters for mean motions, epoch values, and equations in the Alfonsine Tables, and a difference in days of 538949;21,15 from noon, 31 Dec. [year] 0 (JDN 1721423.0000) to 24 July 1476, 8;30h after noon (lDN 2260372.3542), we obtain the Moon's longitude to be 174;17°(text 174;15°). Using the mean motion parameters, epoch values, and equation of centre for Venus in the Alfonsine Tables and the same difference in days since the epoch of the Incarnation, we find the true argument of centre for Venus to be 39;28°(text 39;30°: see Appendix, [8]), and the true argument of anomaly to be 121;30°(text 121;32°: see Appendix, [8]).…”

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“…[11] This is most surprising for, even if there were only 30 minutes between them, they would not even touch each other. [12] All the more so, when [the distance between them] is 3! times that amount.…”

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An Occultation of Venus Observed by Abraham Zacut in 1476

Goldstein

Chabás

1999

Journal for the History of Astronomy

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Occultations of a planet by the Moon happen fairly often but, surprisingly, little attention was given to them in early astronomical literature. Such observations can be used to test the theory of the Moon against the theory of the planet, but testing was by no means a central part of the astronomer's task, as understood before modem times. To be sure, there are dated reports of such occultations in the Babylonian Diaries; I an undated report of the Moon occulting Mars in Aristotle's De caelo ii.12;2 dated reports of the Moon occulting a planet in a medieval Arabic text; and similar reports by Bernard Walther published by Schoener in 1544. 3 On the other hand, there are a few dated reports of occultations of fixed stars by the Moon," and of a star by a planet. 5 The detailed report by Abraham Zacut (1452-1515)6 of an occultation of Venus by the Moon on 24 July 1476 is of considerable interest from several points of view, but in the perspective of late medieval astronomy, the principal interest concerns the way Zacut used this event to support, and to query, various aspects of the theories for planetary motion.Zacut was a major figure in the astronomical community of his day, and his magnum opus, composed in Hebrew in Salamanca, Spain, in 1478, was entitled ha-Hibbur ha-gadol (The great compositions.' This work consists of a set of astronomical tables, preceded by an introduction (or canons) in 19 chapters to explain them. Zacut's canons were translated from Hebrew into Castilian in 1481, with the assistance of the author, by Juan de Salaya who had been professor of astronomy at the University of Salamanca. But Zacut's fame largely depends on a version of his astronomical tables published in Latin in Leiria, Portugal, in 1496, with canons in Latin in some copies, and in Castilian in others." The canons in the edition of 1496 are not the same as those in the Hebrew text of The great composition, and some of these differences are important for our analysis of Zacut's report. This work in Latin was reprinted several times in the sixteenth century with the title Almanach perpetuum.The occultation has not been mentioned until now in the literature on Zacut because it is not included in the edition of 1496 or in the translation by Salaya,? Moreover, it is not found in the three Hebrew MSS that contain copies of his tables. In fact, it is found only in a Hebrew manuscript (MS B) dated 1489, that is, during the lifetime of Zacut, that has the canons but no tables. 10 It is difficult to explain its absence from the other copies of Zacut's work; perhaps Zacut did not see this report as having great value, or perhaps his contempories did not consider it worthy

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An Occultation of Venus Observed by Abraham Zacut in 1476

Goldstein

Chabás

1999

Journal for the History of Astronomy

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“…In fact, the earliest unambiguous evidence for the use of the Alfonsine Tables in the Iberian peninsula comes in a Latin text by Polonius written in Salamanca in the 1460s, and the earliest set of tables in Hebrew from Spain or Portugal that depends on the Alfonsine Tables is that of Zacut, compiled in 1478. 17 There has been some confusion on the identity of Judah ben Asher, for there were two members of the same family with that name, both descendents of a famous rabbi of Toledo, Asher ben Yehiel (d. 1328). One Judah benAsher was his son who died in 1349, apparently a victim of the Black Death; the other was his great grandson who died as a martyr in 1391 during the widespread anti-Jewish riots of that year.18 Again, thanks to Tzvi Langermann, the tables of Judah ben Asher have been identified: they are preserved in the same Vatican manuscript already mentioned, where they are ascribed to "Judah" (MS Heb.…”

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