Sepher Ibronoth [astronomy and calculations of intercalation and the Jewish calender]

BEILIN, ELIEZER.

Johann Christoph Beckmann

Frankfurt on der Oder

1691

Woodcut illustrations of Scales of Justice on f. 6a and b, hand-palm on f. 20b, spherical charts on ff. 23b -25a, mathematical tables and illustrations. Corrections on some charts in an Ashkenazic hand (see ff. 23a and 24a). Verso of the front flyleaf contains a short description of this work in French and the difference between “Chelek” and “Rega”. The section “Luach HaChagaoth” notes the Christian holidays observed in Germany, Poland and Russia, as well as dates of the fairs and market days held throughout the year.

Vinograd, Frankfurt on der Oder 48.

The Jewish calendar is lunisolar; the months are reckoned by the moon and the year by the sun. Thus, the expertise required to make the necessary calendrical adjustments, mandated for religious Jews a proficiency in astronomy. Indeed Maimonides devotes an entire section of his Mishneh Torah to what he lists as a positive commandment “to know how to determine which is the first day of each month of the year.” Consequently, Sepher Ibronoth was prepared by Beilin as a manual “to help an individual fulfill these commandments.” See A. J. Karp, From the Ends of the Earth-Judaic Treasures of the Library of Congress, (1991) pp. 197-8.