Galileo
It was Galileo who made the instrument famous. He constructed his first three-powered spyglass in June or July 1609, presented an eight-powered instrument to the Venetian Senate in August, and turned a twenty-powered instrument to the heavens in October or November. With this instrument he observed the Moon, discovered four satellites of Jupiter, and resolved nebular patches into stars. He published Sidereus Nuncius in March 1610.