Complex sentence: He is perhaps best known for his trigonometric tables and for being Nicolaus Copernicus'sole pupil, who facilitated the publication of Copernicus' "De revolutionibus orbium coelestium" ("On the Revolutions of the Heavenly Spheres").
Split into simpler sentences: He is perhaps best known for his trigonometric tables and as Nicolaus Copernicus's sole pupil. He facilitated the publication of his master's "De revolutionibus orbium coelestium" ("On the Revolutions of the Heavenly Spheres").