 At this great imperial ceremonial gathering in Nuremberg, Celtes was at the same time presented with a doctoral degree.Celtes again made a lecturing tour throughout the empire.In 1489–1491, he stayed in Kraków where he studied mathematics, astronomy and the natural sciences at the Jagiellonian University (at which he enrolled in 1489), and befriended many other humanists such as Lorenz Rabe and Bonacursius.