In his main work 'Oculus artificialis teledriopticus sive telescopium' (EA Nuremberg 1685) Johann Zahn (1631-1707), cleric in the Würzburg praemonstrantensian monastery, provided an early and comprehensive description of the function and application of optical instruments. In splendid copperplate engravings it explains the function of tools like the camera obscura and early forms of telescopes and microscopes. His work furthermore includes depictions of the important solar and lunar maps based on Cherubini.