  The question, Did Simon Marius (1573-1625) observe Jupiter's satellites on
January 8, 1610 (December 29, 1609 in the Julian calendar) is moot, for he did
not disclose his research method and the instrument he used. To resolve this
issue we apply astronomical codes and evaluate the visual performance of a
replica of the telescope that Galileo Galilei (1564-1642) had used.
