Tycho and his great quadrant at Uraniborg. Tinted engraving from Tycho's Astronomiae instaurata mechanica, published in Wansbeck in 1598. Completed in 1582, something like the mural quadrant was evidently planned upon Tycho's arrival on Hveen in 1576, since the accurately aligned wall on which the quadrant was later mounted was built into Uraniborg at the onset. The accuracy of this instrument, based on comparison with eight reference stars, has been estimated to 34.6 seconds of arc.
Here are other noteworthy instruments built by Tycho and his team of instrument builders, listed in chronological order:
Large instruments such as these, with improved sighting devices and measuring scales, as well as Tycho's advanced procedures to correct for atmospheric refraction, allowed him to compute stellar and planetary positions consistently accurate to within seconds of arc. Tycho's determination of the tropical year was too small by about one second, and his determination of the Earth's orbital tilt (which Tycho, committed to the Earth's fixity as he was, referred to as the angle between the ecliptic and the celestial equator) by half a minute of arc.
Tycho left Hveen in 1597, having fallen out of favor with the Danish King Christian IV. Upon settling in Prague he arranged for most of his instrument to be shipped there. After his death, legal battles between Kepler and Tycho's heir led to the instruments being stored away. All but Tychoi's great globe were destroyed in the aftermath of the Bohemian civil war of 1619. The great globe found its way back to Copenhagen, and remained in the University's observatory tower until that tower and all its content were destroyed by fire in 1728. All we know from Tycho's instruments is from his (fortunately elaborate) published writings.
Thoren, V.E. 1973, Journal for the History of Astronomy, 4, 25.
Wesley, W.G. 1978, Journal for the History of Astronomy, 9, 42.
-Written in December 1997, and last revised 8 November 1998, by paulchar@ucar.edu.
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