This is the title page of the Siderius Nuncius (Starry Messenger) of Galileo (1564-1642), published in 1610. The page reads, "The Starry Messenger, Revealing great, unusual, and remarkable spectacles, opening these to the consideration of every man, and especially of philosophers and astronomers; as observed by Galileo Galilei, Gentleman of Florence, Professor of Mathematics in the University of Padua, with the aid of a spyglass, lately invented by him, In the surface of the Moon, in innumerable Fixed Stars, in Nebulae, and above all in four planets swiftly revolving about Jupiter at differing distances and periods, and known to no one before the author recently perceived them and decided that they should be named The Medicean Stars." This book was a report on Galileo's first investigations with a telescope, although the telescope was certainly not "invented" by him. The discussion of the moons of Jupiter was influential in gaining acceptance for the Copernican theory of the solar system.
This page gives Galileo's initial sketches of the surface of the moon, with various craters, and the line between darkness and light clearly visible.