The Bohemian Martin Horky, mathematician, physician and student of astrology, is known mainly for the opposition he made to Galileo’s discoveries. In 1610 he was living in Bologna at the home of the astronomer Antonio Magini (1555-1617), as the latter’s assistant, and was present at the demonstration of the telescope that Galileo performed in that city on his return from a brief stay in Tuscany. Both Horky and Magini cast doubt on the existence of the Medicean Planets, maintaining that what appeared in the telescope was just an optical illusion. On his own initiative Horky went to Modena where he had printed his Brevissima peregrinatio contra Nuncium Sidereum (Modena, 1610), in which he sought by means of the weakest theoretical arguments to deny the real substance of Galileo’s discoveries, and claimed maliciously that the spots seen through the telescope near Jupiter served the sole purpose of satisfying Galileo’s lust for money. Giovanni Antonio Magini, when he found out about Horky’s fiasco, threw him out of his house and let Galileo know that he had had nothing to do with the business. Horky, finding no support in Italy, sought it abroad by writing to Kepler (1571-1630), who however replied to him in the harshest terms. Kepler in fact stated his intention to sever their friendship, and he immediately wrote to Galileo disavowing the Brevissima peregrinatio. Horky’s attack boomeranged, but his was just one of the first manifestations of opposition to Galileo which would soon grow secretly into vast proportions.