Astronomical Images : Triquetum

Theon of Alexandria

Astronomical Images

<p style='text-align: justify;'>This illustration of a parallactic instrument, known as a triquetum in the Middle Ages, was published in Theon's <i>Commentaria</i> (originally compiled c. 370 A.D.) on Ptolemy's <i>Almagest</i>. A manuscript of Theon's <i>Commentaria </i>was presented to Regiomontanus by Cardinal Bessarion, and Regiomontanus intended to produce a translation of it along with the <i>Almagest</i>. He could not carry out either project, however, and this first Greek edition of the <i>Commentaria</i> was due to Joachim Camerarius the Elder, using the manuscript owned by Regiomontanus. The work is preceded by a letter from Camerarius to the Nuremberg Senate. The arrival of Cardinal Bessarion in Vienna (1460) represents a major event in the lives of Regiomontanus and his teacher, Peuerbach, as well as in the history of astronomy. Bessarion was a patron of the mathematical disciplines and greatly promoted the study of Greek ' his native tongue ' in Western Europe. They soon established close contacts lasting throughout their lives. Regiomontanus acquired a remarkable knowledge of Greek and therefore had access to the main mathematical and astronomical works then extant, notably those by Ptolemy.</p>