Which astronomer invented the first usable telescope?

The invention of the first usable telescope is attributed to Galileo Galilei, who significantly improved upon earlier designs. While various forms of telescopes existed prior to his work, Galileo's enhancements allowed for a much more effective observation of celestial bodies. In 1609, he constructed a telescope that could magnify objects up to 20 times, which was revolutionary for its time. This advancement enabled him to make groundbreaking discoveries, such as the moons of Jupiter, the phases of Venus, and detailed observations of the Moon's surface.

Galileo's contributions laid crucial groundwork for modern astronomy. His approach of systematic observation and application of the scientific method marked a departure from earlier philosophical approaches to understanding the universe. His work demonstrated the power of telescopic observation and supported the heliocentric model of the solar system, validating theories that were previously considered controversial. This makes him a pivotal figure in the history of science.