Willebrord Snellius · 1618
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The Coeli et siderum in eo errantium Observationes Hassiacae is the first printing of the observations made at Kassel under Landgrave Wilhelm IV of Hesse. Willebrord Snellius edited it and dedicated it to Wilhelm’s son Maurice.
The Kassel observations of the planets come first. The book adds a selection from Tycho Brahe’s Bohemian observations and, under its own signatures, the Nuremberg observations of Regiomontanus and Bernhard Walther. Around them are Johann Schöner’s notes on the cross-staff, tables, a passage from Kepler on Walther’s refraction, and Regiomontanus’s sixteen problems on the size and distance of comets. Snellius addresses the reader directly, comparing the results.
Together with Tycho’s own records, the Kassel series is the chief body of precision observation from before the telescope.
The Bavarian State Library copy ends at printed page 116, although its title page announces the Nuremberg observations, so this edition takes that second sequence from the copy in the ETH-Bibliothek Zürich. Snellius’s own Eratosthenes Batavus is also in this collection.