CHRISTMANN, Jacob (1554-1613). Observationum solarium libri tres. In quibus explicatur verus motus solis in zodiaco: & universa doctrina triangulorum, ad rationes apparentium coelestium accommodatur. Basel: Lazarus Zetzner, 1601.

Fine first edition of Christmann's first astronomical publication, on spherical geometry as applied to his solar observations, complete with folding table. The author, a professor of oriental languages at Heidelberg and the second teacher of Arabic in Europe, had made the observations over several years using a sextant of his own design. Christmann's interest in astronomy was partially inspired by his inheritance of the library of Georg Rheticus, which had been in the keeping of his devoted student Valentinus Otho. This collection contained not only trigonometric tables more extensive than those that Rheticus had published in the 1596 Opus Palatinum, but also the original manuscript of Copernicus’s De revolutionibus orbium coelestium.

The present work, dedicated to Tycho Brahe's nephew, begins with a chapter on the construction and use of astronomical instruments, a discussion of solar parallax and observational problems and errors, and methods and techniques of solar observations. This is followed by a history of the solar observations of Brahe and Kepler, and a solar ephemeris for 1597 based on Brahe but corrected with Copernicus’s observations. Christmann then presents his own solar tables, and then concludes with a discussion of prosthapharesis and the calculation and application of trigonometric tables. Rare at auction, RBH only records 3 copies, none in a contemporary binding and only one in the last 50 years—the incomplete Macclesfield copy. Houzeau and Lancaster 2883; Zinner 3884.

Quarto (220 x 159mm). Large folding letterpress chart; several diagrams in text (evenly toned). Contemporary yapped vellum, blue edges.