A 17th century illustration of the constellation of Cassiopeia

The constellation of Cassiopeia, engraved by Alexander Mair for Bayer's 'Uranometria', a star atlas that shaped the way the heavens would be perceived for more than two centuries.

Johann Bayer (1572-1625), an Augsburg lawyer, was an amateur astronomer in the years just prior to the invention of the telescope. His most important innovation was a new system of identifying stars by Greek and Roman letters, known today as the Bayer designation. His 'Uranometria' ('Measuring the Sky'), first published 1603, was the first celestial atlas to contain a chart of the stars in the Southern Hemisphere.