Isaac Argyros mathematician, astronomer, and theologian; born Thrace? between 1300 and 1310, died ca.1375. A student of Nikephoros Gregoras, the monk Argyros was the leading Byz. champion of Ptolemaic astronomy in the 1360s and 1370s. He wrote a Construction of New Tables and a Construction of New Tables of Conjunctions and Oppositions (of the sun and moon), for both of which the epoch is 1 Sept. 1367. In them he recomputes for the Roman calendar and the longitude of Constantinople the mean motions of the sun, moon, and planets, and the syzygies that Ptolemy had tabulated in the Almagest according to the Egyptian calendar and the longitude of Alexandria. These tables were soon plagiarized and criticized by John Abramios. In 1367/8 Argyros wrote a treatise on the astrolabe, closely based on the similar treatise of Gregoras. In late 1372 he dedicated a work on the computus to Andronikos Oinaiotes (A. Mentz, Beiträge zur Osterfestberechnung bei den Byzantinern; in this work he indicates that he was at Ainos in Thrace in 1318]. He also wrote scholia on Theon, but did not write, as has been alleged, the anonymous Instructions for the Persian Tables.
Argyros's mathematical works include one on the square roots of nonsquare numbers]; a treatise based on Heron's Geometrics concerning the reduction of nonright to right triangles and other geometrical problems, composed in 1367/8; and a Method of Geodesy, also based on Heron. He also wrote scholia to Ptolemy's Geography and edited with scholia his Harmonics.
Like Gregoras, Argyros supported Barlaam of Calabria in the Palamite controversy. He wrote three anti-Palamite treatises, including an attack on Theodore Dexios's concept of the light on Mt. Tabor.