Anonymous ID: c8c666 July 23, 2019, 2:48 a.m. No.7143900   🗄️.is đź”—kun   >>3976

>>7143878

 

The ASTROLABE was the precursor to the mariner's sextant. Consisted of a circular stack of sliding features all embedded within a disk called a “mater”. A round plate containing a two-dimensional projection of the Earth’s latitudinal lines sat within the mater and, over that plate, another circular feature called the “rete” contains the locations of certain well-known stars in the sky. Over that, a straight rule pivoted around to line up with time measurements along the edge of the mater. And on the back of the whole thing, a pivoting sight helped find the altitude of a star—often the starting point of a calculation for charting a destination on the open seas.