that it looked like an ordinary star—and it describes the star's place in the heavens accurately, and its variations in light and colour. Even though Tycho made some remarks about the astrological significance of the star, he did so in a way which shows that he did not himself consider this the most valuable portion of his work. To appreciate his little book perfectly, it is desirable to glance at some of the other numerous books and pamphlets which were written about the star, and of most of which Tycho himself has in his later work (Progymnasmata) given a very detailed analysis, devoting nearly 300 pages to the task. It would lead us too far if we were to follow him through them all, but it will not be without interest briefly to describe what some of the more rational of his contemporaries published about the star, and to what absurdities a fervid imagination led some of the common herd of scribblers.
At Cassel the star was observed by Landgrave Wilhelm IV., an ardent lover of astronomy, of whom we shall hear more in the sequel. He did not hear of the star till the 3rd December, and took observations of its altitude in various azimuths from that date and up to the 14th March following. From the greatest and smallest altitude Tycho found afterwards a value of the declination differing less than a minute from that found by himself. From the azimuths and altitudes observed at Cassel Tycho deduced the right ascension and declination: the single results for the latter are in good accordance inter se, while those for right ascension differ considerably, the greatest difference being more than 2°. Tycho justly concludes that this must be caused by the bad quality of the clock employed by the Landgrave, who merely gave the time of observation in true solar time, without furnishing the means of correcting for the error of his clock. In a letter to Caspar Peucer, the Landgrave stated that the star might have a parallax not exceeding 3′,
