 In 1774 he designed one of the earliest mechanical calculators of which two are known to have survived to the present day.A renowned clockmaker, several horological museums display his works, including the Deutsches Uhrenmuseum which contains a mechanical orrery (planetarium) and a Weltmaschine by the "Priestermechaniker (priest mechanic)".According to Reinhard Breymayer, Friedrich Schiller's verses "Brüder - überm Sternenzelt/ muß ein lieber Vater wohnen" ("Brothers, above the starry canopy/ There must dwell a loving Father"), reflecting the poet's Philosophy of Love, are a reference to the astronomer and pastor Hahn's Theology of Love.