Astronomical Images : Theory of the motion of the eighth sphere

Johannes Schoener

Astronomical Images

<p style='text-align: justify;'>Johannes Schoener (1477-1547) was a priest and later a teacher of mathematics, who had a strong interest in astronomy and astrology. He assembled a printing shop in his house in Bamberg, where he oversaw each stage of the printing process, from setting the type and carving the woodblocks for illustration to binding the final product. He produced many valuable editions of previously unpublished works by many eminent astronomers of the fifteenth century, including Regiomontanus' <i>De cometae magnitudine ... problemata XVI</i> (1531), as well as publishing his own works. He also made his own globes, which he issued alongside some of his printed books, and his cartographic work was influential to later map-makers such as Gemma Frisius and Gerard Mercator. In 1521 Schoener put his printing press to use for the publication of his <i>Aequatorium astronomicum</i>, in which he employed movable paper disks to represent the movement of the planets. The reader was expected to cut out the templates provided by Schoener and assemble the parts to create a moveable paper instrument, from which planetary positions could be calculated in accordance with Ptolemaic cosmology. After Schoener's death in 1547, his son Andreas published his father's mathematical works under the title <i>Opera mathematica</i> (1551); this copy of the <i>Aequatorium astronomicum</i> is from the revised and enlarged second edition of the <i>Opera mathematica</i>, published in 1561. This diagram gives an overview of the theory of the eighth sphere, highlighting the two little oscillating circles which govern its accession and recession, also known as trepidation.</p>

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