Galilei invented the telescope (i.e. the refractor) in 1609, which of course was a gigantic step for the astronomical research. But as a matter of fact, the technology was known much earlier, for instance by Roger Bacon in the thirteenth century, who describes the mirror telescope fully and clearly in his Opus Majus. But as an Aristotelian he probably saw no reason to make new instruments for astronomical observations - everything was already known in that field! That maybe says something about the strength of "the Aristotelian dogma". However, Tycho, not being an Aristotelian, designed his own instruments of high precision and stability, essentially more reliable than other older or contemporary instruments. For instance, his transversal system made the reading more accurate. Most of his instruments were rigidly and permanently mounted, for instance the famous mural quadrant at Uraniburg, which made long series of comparable observations possible. Considering that the observations were made with the unarmed eye, Tycho's multiplicity of instruments were probably close to what can be achieved in this way. Tycho has in full detail described all his instruments in his book "Astronomiæ Instauratæ Mechanica" (1598). This picture from the book illustrates the great steel quadrant from 1581. In 1588 it was modified and moved from Uraniburg to Stellæburg.

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Lund Observatory, Box 43, SE-221 00 Lund, Sweden Visiting address: Sölvegatan 27 Phone: +46 46 22 27300, Fax: +46 46 22 24614 Publisher: Leif Lönblad E-mail: webmaster@astro.lu.se Last updated: 2002, March 19