Sidereus Nuncius
The first telescopes appeared in the Netherlands in 1608 when Middelburg spectacle-maker Hans Lippershey tried to obtain a patent on one. By 1609 Galileo had heard about it and built his own improved version. He probably was not the first person to aim the new invention at the night sky but his was the first systematic (and published) study of celestial bodies using one. One of Galileo's first telescopes had 8x to 10x linear magnification and was made out of lenses that he had ground himself. This was increased to 20x linear magnification in the improved telescope he used to make the observations in "Sidereus Nuncius".
Zacharias Janssen
Over the years there have been claims Zacharias Janssen invented the telescope and/or the microscope in Middelburg between 1590 and 1618. Zacharias worked for some period of his life as spectacle-maker (a very competitive and secretive trade) and at one time lived next door to Middelburg spectacle maker Hans Lippershey, also claimed to have invented the telescope. Janssen's attribution to these discoveries is debatable since there is no concrete evidence as to the actual inventor, and there are a whole series of confusing and conflicting claims from the testimony of his son and fellow countrymen.