Astrolabe or equiangular

With the use of an equiangulator or astrolabe, it is possible to calculate the angle between the horizontal surfaces and celestial bodies, the azimuth of a star and the exact time.

According to historical sources, this device was initially invented by Eratosthenes in the year of 250 B.C. Whereas, the "Mariner`s Astrolabe" was invented in Greece in the XV century, by Greek astronaut Apollonius. In Europe, astrolabes began to be used for navigational purposes in the XV-XVIII centuries. They are considered to be the predecessors of sextants.