EXPERIMENTING WITH PAPER INSTRUMENTS IN FIFTEENTH AND SIXTEENTH-CENTURY ASTRONOMY: COMPUTING SYZYGIES WITH ISOTEMPORAL LINES AND SALT DISHES.

The article examines astronomers' use of an obscure paper astronomical instrument when calculating syzygies in the 15th and 16th centuries. Syzygies are computations made by astronomers in order to establish the straight-line positioning of the Earth, Sun, and Moon, and are therefore useful when studying eclipses. The author describes the design and construction of this instrument. He then goes on to discuss the use of the instrument's graphical design and computation algorithm. The author then presents astronomical computations developed by his own use of the instrument.