What was the highest magnification of Galileo's best telescope?

Galileo’s best telescope magnified objects about 30 times. That was a remarkable achievement for early seventeenth-century optics, even though the instrument produced narrow, blurry, and distorted views by modern standards.

Galileo built and repeatedly improved refracting telescopes after learning of the Dutch telescope in 1609. His most powerful documented instrument was about 980 millimetres long and used a converging objective lens with a diverging eyepiece. By refining the lenses and using an aperture stop to reduce optical aberrations, he reached roughly 30× magnification.

That modest-sounding figure was enough to transform astronomy. Galileo observed mountains and craters on the Moon, the phases of Venus, sunspots, and four moons orbiting Jupiter. “30 times” is normally rounded because the performance of these handmade instruments was described approximately rather than with modern laboratory precision.