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".
Newton's reflector
There has been much confusion and dispute concerning the telescopes that Newton built, but it is now clear that his first telescope was a prototype that he constructed in 1668. This was seen only by a few friends at Cambridge and very little is known of it. This prototype had a mirror a little over an inch in diameter, probably 1.3 inches, and around 6 inches in length. Newton seldom referred to this prototype in later years and so his second scope is often called his first.