Tycho Brahe

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Tycho Brahe : biography

14 December 1546 – 24 October 1601

After Frederick died in 1588 and his 11-year-old son, Christian IV, succeeded him, Tycho’s influence steadily declined. After several unpleasant disagreements, Tycho left Hven in 1597. The instruments he had used in Uraniborg and Stjerneborg were depicted and described in detail in his book Astronomiae instauratae mechanica, first published in 1598.

He moved to Prague in 1599. Sponsored by Rudolf II, Holy Roman Emperor, Tycho built a new observatory in a castle in Benátky nad Jizerou, 50 km from Prague, and worked there for one year. The emperor then brought him back to Prague, where he stayed until his death. Tycho received financial support from several nobles in addition to the emperor, including Oldrich Desiderius Pruskowsky von Pruskow, to whom he dedicated his famous "Mechanica". In return for their support, Tycho’s duties included preparing astrological charts and predictions for his patrons on events such as births, weather forecasting, and astrological interpretations of significant astronomical events, such as the supernova of 1572 (sometimes called Tycho’s supernova) and the Great Comet of 1577.Adam Mosley and the Department of History and Philosophy of Science of the University of Cambridge. . 1999. Retrieved 2008-10-02

Introduction to the New Astronomy (1588)

The year 1588, which saw the death of his royal benefactor, saw also the publication of a volume of Tycho’s great work Astronomiæ Instauratæ Progymnasmata or "Introduction to the New Astronomy". The first volume, devoted to the new star of 1572, was not ready, because the reduction of the observations of 1572-3 involved so much research to correct the star places for refraction, precession, the motion of the sun etc., and was not completed in Tycho’s lifetime, but the second volume, devoted to the comet of 1577, was printed at Uraniborg and some copies were issued in 1588. Besides the comet observations it included an account of Tycho’s system of the world.Walter William Bryant, Macmillan Co. (1920) p.24 The third volume was to treat the comets of 1580 and following years in a similar manner, but it was never published, nor even written, though a great deal of material about the comet of 1585 was put together and first published in 1845 with the observations of this comet.John Louis Emil Dreyer, A. & C. Black (1890) p.162-3

Tycho’s observational astronomy

Mural quadrant (Tycho Brahe 1598)

Tycho’s observations of stellar and planetary positions were noteworthy both for their accuracy and quantity.Noel Swerdlow, Astronomy in the Renaissance, pp. 187-230 in Christopher Walker, ed., Astronomy before the Telescope, (London: British Museum Press, 1996), pp. 207-10. His celestial positions were much more accurate than those of any predecessor or contemporary. Rawlins (1993, §B2) asserts of Tycho’s Star Catalog D, "In it, Tycho achieved, on a mass scale, a precision far beyond that of earlier catalogers. Cat D represents an unprecedented confluence of skills: instrumental, observational, & computational—all of which combined to enable Tycho to place most of his hundreds of recorded stars to an accuracy of ordermag 1′!"

He aspired to a level of accuracy in his estimated positions of celestial bodies of being consistently within 1 arcminute of their real celestial locations, and also claimed to have achieved this level. But in fact many of the stellar positions in his star catalogues were less accurate than that. The median errors for the stellar positions in his final published catalog were about 1′.5, indicating that only half of the entries were more accurate than that, with an overall mean error in each coordinate of around 2′.Rawlins 1993, p. 12Rybka 1984 found a mean error of some 3′ for nonbright stars by comparing star Catalogue D with "the modern FK4 star catalogue" values. Although the stellar observations as recorded in his observational logs were more accurate, varying from 32.3" to 48.8" for different instruments,Walter G. Wesley, Journal for the History of Astronomy, 9(1978): 42-53, table 4. systematic errors of as much as 3′ were introduced into some of the stellar positions Tycho published in his star catalog – due for instance, to his application of an erroneous ancient value of parallax and his neglect of polestar refraction.Dennis Rawlins, "Tycho’s 1004 Star Catalog", (1993), p. 20, n. 70. Incorrect transcription in the final published star catalogue, by scribes in Brahe’s employ, was the source of even larger errors, sometimes by many degrees.(i)Thoren 1989 Tycho Brahe says: "[the accuracy of the 777 star catalogue C] falls below the standards Tycho maintained for his other activities….the catalogue left the best qualified appraiser of it (Tycho’s eminent biographer J.L.E. Dreyer) manifestly disappointed. Some 6% of its final 777 positions have errors in one or both co-ordinates that can only have arisen from ‘handling’ problems of one kind or another. And while the brightest stars were generally placed with the minute-of-arc accuracy Tycho expected to achieve in every aspect of his work, the fainter stars (for which the slits on his sights had to be widened, and the sharpness of their alignment reduced) were considerably less well located." (ii) Hoskin’s 1999 p101 concurs with Thoren’s finding "Yet although the places of the brightest of the non-reference stars [in the 777 star catalogue] are mostly correct to around the minute of arc that was his standard, the fainter stars are less accurately located, and there are many errors." (iii) The greatest max errors are given in Rawlins’ 1993. They are in descending order a 238 degrees scribal error in the right ascension of star D723; a 36 degrees scribal error in the right ascension of D811 (p42); a 23 degrees latitude error in all 188 southern stars by virtue of a scribal error (p42 M5); a 20 degrees scribal error in longitude of D429; and a 13.5 degrees error in the latitude of D811.