One of the earliest instruments used by astronomers. Originally they were spherical in shape and consisted of divided metal circles corresponding to ecliptic, meridian, etc. with which the position of the Sun, Moon and Stars could be measured with fair accuracy. Hipparchus, Greek Astronomer, used one before 100 B.C. Tycho Brahe, Danish astronomer who died in 1601, had one similar to that illustrated. Portable astrolabes varying in size from two inches to a foot were first made in the East in 15th Century and later were used in India, Persia and Arabia.
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