Complex sentence: His pupil Johannes Schöner made yet unpublished data of Mercury observations from Walther available to Nicolaus Copernicus, 45 observations on total, 14 of them with longitude and latitude.
Split into simpler sentences: His pupil Johannes Schöner made unpublished data of Walther's observations of Mercury available to Nicolaus Copernicus.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.