Before the invention of the telescope, the Danish astronomer Tycho Brahe revolutionized astronomy by establishing the importance of accurate observations. He invented an improved sextant and used it to make precise observations of the positions of stars and planets.
Brahe completely recalculated Ptolemy’s astronomical tables, which contained many errors, and catalogued over one thousand stars during his lifetime. He built Europe’s first observatory and taught the art of observation to a generation of astronomers.
In 1572 Brahe made careful observations of a “new star” (actually a supernova) that appeared suddenly in the constellation Cassiopeia. He showed that the object was not in the Earth’s atmosphere but was actually beyond the orbit of the moon. This discredited the prevailing theory that the heavens are static and unchanging.