Galileo Galilei did not invent the telescope. The honor is usually reserved for Hans Libbershey, a Dutch eyeglass maker, who was at least the first person to apply for a patent, in 1608. But Galileo was a very early adopter, and improver, of the instrument. In 1609, he made the drawings above “from life,” the very first realistic renderings of the Moon (now housed at the Biblioteca Nazionale Centrale in Florence). Prior to Galileo’s illustrations, Rice University’s Galileo Project informs us, “virtually no one bothered to represent the Moon with its spots the way it actually appeared.” This was in part due to a belief, derived from Aristotle, that the Moon, and every other astral body, was perfect, in contrast to the Earth’s irregularities. After his observations, Galileo planned the following year to create an entire series of illustrations, presumably “to show how the shadows of individual features changed with the illumination.” This, however, became unnecessary since “even the Jesuit fathers in Rome were convinced that that the Moon’s surface was uneven.”
Galileo did incorporate his findings into his groundbreaking treatise Sidereus Nuncius (“The Starry Messenger”), published in Latin in March of 1610, in which he promoted the Copernican heliocentric theory with copious evidence (and for which he was eventually placed under house arrest in 1633). In his treatise, he explained his observations of a coruscated, pitted, and mountainous Moon and included several additional drawings, such as those above and below. (He also made scores of drawings of Jupiter and several constellations.) Like many scholars of his day, Galileo was also an accomplished draftsman, as you can plainly see. And like scholars still today, he was required to excel at the fine art of self-promotion, forced not only to compete with his contemporaries, but also to persuade his patrons as well as mollify the institutional authorities.
In title page of Sidereus Nuncius, Galileo introduces himself as “Florentine patrician and public mathematician of the University of Padua” and touts his accomplishments in devising a “spyglass” and observing “the face of the Moon, countless fixed stars, the Milky Way, nebulous stars….” He is especially proud, however, of his discovery of four moons of Jupiter, which he calls “four planets.” These satellites, he writes, were “unknown by anyone until this day,” and he names them “the Medicean Stars” after his influential patron Cosimo Il de-Medici, duke of Tuscany. It is a dedication, astronomer Nick Kollerstrom argues, that helped propel Galileo to his position as the “court philosopher” of Florence. In the rough sketch of the waxing Moon below, made in January, 1609, Galileo includes at the top a draft of an astrological nativity of his wealthy sponsor.