Astronomical Images : Astrolabe: a latitude plate with lines of equal azimuth radiating from the observer's zenith

Johann Stoeffler

Astronomical Images

<p style='text-align: justify;'>Johann Stoeffler (1452-1531) was a mathematician, astronomer and instrument-maker who was appointed to the chair of mathematics and astronomy at the University of Tuebingen. His <i>Elucidatio fabricae ususque astrolabii</i> was one of the most influential books published on the astrolabe, with editions extending from 1513 into the seventeenth century. This edition of 1524 was published by Stoeffler's friend Jacob Koebel, who also contributed an address to the reader. Stoeffler devotes Part 1 to the construction of the components of an astrolabe, including marking the lines on the latitude plates; setting out the rete (with the star positions in Latin and Arabic); applying the calendar scale, the shadow square and the unequal hours lines to the back; making the rule, alidade, axis and suspension shackle. Stoeffler also discusses an horary quadrant for equal hours, the use of the shadow square in surveying, and the astrological applications of the astrolabe. Such was the currency of his account that 'Stoeffler's astrolabe' came to stand for fixed-latitude astrolabes, as distinct from the universal ones. Here, the figure shows a latitude plate with lines of equal azimuth radiating from the observer's zenith.</p>