The third chapter describes the appearance of the star, the gradual fading of its light, the variation of colour; how it was seen by carriers, sailors, and similar people, a good while before the astronomers in their chimney-corners heard of it; then branches off into a mythological account of Queen Cassiopea, and gives a map of the constellation with the star in it. Tycho refers to the Aristotelean idea of the unchangeable nature of the heavens, and to the star of Hipparchus, which he believes to have been similar to his own star, and then to that of the Magi, which he says could not have been a star in the heavens, since it showed the way to a particular town, and even to a house, and was only seen by the wise men. He therefore summarily dismisses the idea that the star in Cassiopea should signify the return of Christ. Lastly, he mentions the stars said by Cyprianus Leovitius to have appeared in the years 945 and 1264. All these subjects we have dealt with in sufficient detail in the chapter on the new star, where the book of which we are now summarising the contents is frequently quoted.
In the fourth chapter are given descriptions and illustrations of the sextant with which he observed the star, and of the great quadrant at Augsburg. This chapter also contains the measured distance of the new star from twelve stars in Cassiopea, the distances inter se of most of these stars (from observations made at Hveen in 1578 and 1583), and a number of observations made with the Augsburg quadrant. As this instrument was designed and constructed by Tycho, he naturally wished to prove its excellence, and inserted a number of observed declinations of circumpolar stars (which give values for the latitude of Göggingen agreeing inter se within a minute), and the declinations of six zodiacal stars in equally good accordance with the results obtained at Hveen.
In the fifth chapter the co-ordinates of the star both
