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Who precisely invented the telescope is a somewhat fuzzy question. Since before recorded history, people have been playing with simple lenses made from rock crystal (quartz), and it seems that the basic concept of a telescope was recognized in 1230 or earlier. The late 13th century saw the invention of convex lenses for correcting long-sightedness, whereas concave lenses for near-sightedness were invented in 1451 by Nicholas of Cusa. Since a basic telescope is just a combination of a convex and concave lens in a mounting tube, the basic possibility was there. In fact, various writings from late 16th century England hint that telescopes may have been developed and used there by at least a few individuals.
Yet it wasn’t until 1608 in the Netherlands that telescopes really took off. The credit for inventing the telescope traditionally goes to three people: Hans Lippershey and Zacharias Janssen, spectacle-makers working together in the town of Middleburg, and Jacob Metius of Alkmaar. Soon after this, telescopes began to be produced in greater numbers, and spread across Europe as novelty items. Thus 1608 is the officially recognized year for the telescope being invented. These early telescopes only magnified faraway objects by a factor of about three.
When telescopes were still extremely new, in 1609, the soon-to-be-famous Italian astronomer and physicist, Galileo Galilei, heard of the basic operating concept behind the telescope while visiting the town of Venice. As soon as he returned home to Padua, he immediately built one, simply by putting a convex and concave lens together in a tube. He made an improved version, and showed it to the lord of Venice, Leonardo Donato, who was very impressed. Galileo was thereafter settled for life at his lectureship, and his salary was doubled.
Galileo improved the telescope until it had a magnifying power of thirty-three diameters. He then used his telescope to discover the moons of Jupiter, spots on the Sun, the phases of Venus, and the hills and valleys of the Moon. These discoveries made him famous to this day, and thus telescopes of this design are still called Galilean telescopes.
The other major type of telescope, the reflecting telescope, was invented by the English surveyor Leonard Digges in the mid 16th century, but it was relatively impractical and never became widespread in his day. It was left up to Isaac Newton, the great physicist, who in 1669 constructed the first practical reflecting telescope.