CLAVIUS Christoph (Stefan BATORY), Gnomonices libri octo inquibus non solum horologiorum solariū, sed aliarum quoque rerum,

Gnomonices libri octo inquibus non solum horologiorum solariū, sed aliarum quoque rerum,

quae ex gnomonis umbra cognosci possunt, descriptiones Geometrice demonstrantur. Avctore Christophoro Clavio Bambergensi Societatis Jesv. Maiorum permissu. Romae 1581. apvd Franciscum Zanettow MDLXXXI (1581). (34.5 x 23 cm), f. [8], pp. 655, [3], title in copperplate, numerous woodcuts in the text, tables, date and printer repeated at the end. period leather binding.
(Estr. T. 14). Dedication to King Stefan Batory (Stephano Poloniae Regi potentissimo, Magnoq Lithuaniae Duci, etc.). FIRST EDITION of this masterpiece on the theory and construction of sundials. Clavius considers the astronomical foundations, geometric theory and various methods of sundial construction that preoccupied many mathematicians at the time. The problems of sundial construction were related to the study of perspective and shadows, which painters such as Albrecht Dürer were also interested in. The Latin name Christopher Clavius is the only known name of this Jesuit mathematician and astronomer, whose name in German is unknown. Born in Bamberg, he entered the Jesuit order in 1555. He studied at the Collegio Romano, and in 1579 was given the task of figuring out how to adjust the calendar to the actual seasons. The result, based on the work of Erasmus Reinhold and Aloysius Lillius, was a reformed calendar that was approved by Pope Gregory XIII. Adopted in 1582, the Gregorian calendar is still used as the common calendar of today's Western world. "It summarizes everything that was known about gnomonics" (Honeyman). Work decorated with numerous geometric woodcuts. Traces of non-moisture and soiling, two penultimate pages in a handwritten copy from the period, card 643/4 missing. Binding: white leather with blind embossing, on the spine an inscription (abbreviated) of the author and title, and numbers VII and 14. Abrasions of the binding (edge detail) and soiling. Good condition. Very rare.