Armillary astrolabe

[Opera Laboratori Fiorentini]

This instrument, already described by Ptolemy in the Almagest, was thereafter used by many Renaissance astronomers, and finally included by Copernicus in On the Revolutions. To use this instrument, one has to move two rings exactly toward the Sun. Then, turning the innermost rings, and looking through the sights of the instrument, one can measure the longitude and the latitude of the Moon. This procedure can be iterated to measure the longitude and latitude of the planets and the stars.

.................................