Karl Schwarzschild, Annie J. Cannon and Cornelis Easton: The honorary PhDs of Jacobus C. Kapteyn

Honorary degrees and particularly doctorates are important instruments to enhance the standing of universities and professors, in addition to receiving these as a measure of a scientist's recognition. Jacobus C. Kapteyn from the University of Groningen in the Netherlands, one of the most prominent astronomers of his times, received three of these and has persuaded his university to award at least three, possibly five. I examine the background of the selection of the latter in view of developments in Kapteyn's time in his career, international astronomy and political and cultural circumstances.