Its true that people in Copernicus' time and area were nothing but Catholics, but it was the Germans who overwhelmingly switched to Martin Luther's Prostentantism NOT the Poles.  The fact that ALL of Copernicus' family were staunch Catholics while most Germans in the area were being swept up with the proud German Martin Luther's Prostentant religion shows Copernicus was all Polish.  Also Copernicus' Uncle's German name means nothing since many Poles had German names and spoke German.  Just like the philosopher Friedrich Nietzsche who had a German name, spoke perfect German but was ethnically Polish.