“Mathemata mathematicis scribuntur.”
is the original Latin of Copernic which is easily translated as
“Mathematics is written for mathematicians.”
but Edward Rosen chose to translate this famous passage as
“Astronomy is written for astronomers.”
Obviously "astronomy" is not the author's word and also it is generally agreed that there was no mathematicians around if the word denotes what we mean today. The quote is commented by Westmann (The Copernican Question, 2011, p.37):
Edward Rosen chose to translate this famous passage as "Astronomy is
written for astronomers,” straining to get the text’s language into
agreement with his own assumptions about how Copernicus conceived his
role. But neither my rendering nor Rosen’s is quite satisfactory
without further qualification. For the historian to call Copernicus a
mathematician evokes confusing associations with the current domain
of meaning, in which mathematicians may or may not test hypotheses
against the physical world; and to call him an astronomer overrides
the meaning that mathematicus had in the sixteenth century, that is,
someone skilled in any subject that involved mathematics—for example,
optics, music, statics, or astrology.
This is rather early in his book and it is mostly a rhetorical move: obviously De revolutionibus is not for someone skilled in optics, music or statics.
History of Science tends to get badly distorted when people refuse to acknowledge that from Hellenistic times down to Galileo astrology was a major branch of interest. Attempts to erase it have been made first by devout Christians and later by the Enlightenment. Westman has made a significant contribution to put things back where they belong (but that is an other topic).
Rosen's rendering needs qualification as the Latin words astronomia/astronomer appear in Osiander's preface. Latin translation of Aristotle use the word 'astrologia' for which modern editions put 'astronomy'. Mathematics is referred to as 'geometry' and this is also the meaning of the (fake) motto "Let no one untrained in geometry/ageometretos/ enter here". The distinction "mathematics" vs. "geometry" is clearly present in Classical Latin as seen it the Codex Justinianeus (9.18.0, quoted above).
So, the textual problem is how much astrology was the 16th.c. Church willing to allow? There is no good answer, at least not before Galileo's trial. Liberal minded authorities tended to present it as 'mathematics' while zealots saw it as noxious false prophecies. Copernic composed his dedication well informed for whom it was written.