Astronomy
Walther further brought into prominence the effects of refraction in altering the apparent places of the heavenly bodies, and substituted Venus for the moon as a connecting-link between observations of the sun and stars. Resultantly, his observations are the most precise prior to Tycho Brahe.
His pupil Johannes Schöner made unpublished data of Walther's observations of Mercury available to Nicolaus Copernicus. There were 45 observations in total, 14 of them with longitude and latitude. Copernicus used three of them in "De revolutionibus", giving only longitudes, and erroneously attributed them to Schöner.
These values differed slightly from the ones published by Schöner in 1544 in Observationes XXX annorum a I. Regiomontano et B. Walthero Norimbergae habitae, ., a collection of the astronomical observations of Regiomontanus and Walther, as well as manuscripts of Regiomontanus, which had been in the possession of Walther. In 1618, Willebrord Snell noted them as an appendix to his Observationes Hassiaceae.
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