This astrolabe was made in Germany in the 17th century, a time when astrolabes were already on the verge of decline in the West. It is remarkable for its fanciful stellar markers (usually just sharp pointers, for the sake of precision) and for including the comet of 1618 and the novae of 1572, 1600, and 1604. (Adler Collections, M-34.)
Astrolab (dated century): This was for measuring the altitude of heavenly bodies above the horizon, and so determining (among other things) the time of day or night. Readings are taken by means of rotatable alidade, a diametrical rule with sights.
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