Astronomical Images : Quadrant

Tycho Brahe

Astronomical Images

Having lost the favour of the Danish court in the latter years of the sixteenth century, Tycho Brahe published his Astronomiae instauratae mechanica in 1598 as part of a strategy to procure royal patronage elsewhere. Addressed to his eventual patron, Holy Roman Emperor Rudolph II, the work lavishly described and illustrated the innovative astronomical instruments that Tycho had designed and constructed on the island of Hven, the site of his astronomical programme under the patronage of the Danish court. Though primarily focused on his instruments, the work also included an appendix on 'architectonic structures suitable for astronomical observations', which offered descriptions and illustrations of his two observatory buildings, as well as a map of Hven based on his own observational data. As such, the Mechanica offered not simply an overview of Tycho's instruments, but rather a presentation of his whole astronomical programme for which he was seeking financial support. This is an image of one of the many quadrants that Tycho constructed during his years on Hven. The horizon ring GHIK beneath the quadrant arc itself enabled azimuths measurements to be made in addition to altitude. Furthermore, the square ADEF within the frame of the quadrant could be used to make measurements of the height and breadth of terrestrial objects; Tycho mentions Peuerbach's Geometrical Square as the inspiration behind this feature. Like many of his instruments, Tycho emphasises that it is made from light materials in order that it is both easier to operate and easier to transport. Similarly, it can be easily taken apart and reassembled, again facilitating transportation; for this reason, Tycho referred to this instrument as his 'portable azimuth quadrant'. Interestingly, Tycho emphasises the limitations of this instrument in terms of its precision, asserting that larger, more precise instruments are required when high levels of accuracy are required.