In October 1608, a Flemish spectacle-maker by the name of Hans Lippershey applied for a patent for his spyglass which allowed distant objects to be seen as distinctly as if they were nearby. Knowledge of it quickly spread around Europe and soon such telescopes could be bought quite easily. In England, the mathematician Thomas Harriot used one to make what are believed to be the first telescopic observations of the Moon. The first known (rather crude) drawing shown in Figure 9.1 was dated 26 July 1609, followed later with an impressive map of the Moon. Harriot did not publicise his observations and, as a result, it is widely thought that the first astronomical drawings made using a telescope were made by Galileo Galilei.

The spyglass came to the attention of Galileo in July 1609; he quickly worked out the principle of the telescope and built himself an eight-power telescope. Grinding his own lenses and optimising the shape of the objective lens, he gradually improved the power and image quality of the telescope and began to observe the heavens, making his first astronomical observations in the autumn of 1609. In March 1610, he published The Starry Messenger, which described his observations of the Moon and planets – particularly those of Jupiter and its moons: