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".
Cornelis Drebbel
One of the optical devices some historians believe Drebbel invented when he was working for the Duke of Buckingham was the compound microscope. The device appeared in Europe around 1620 with the earliest account being Dutch Ambassador Willem Boreel's 1619 visit to London where he saw a compound microscope in Drebbel's possession, described as an instrument about eighteen inches long, two inches in diameter, and supported on 3 brass dolphins. In 1621 Drebbel had a compound microscope with two convex lenses. Several of his contemporaries, including Christiaan Huygens, credited the invention of the compound microscope to Drebbel. The invention has many counter claims including Dutch spectacle-maker Johannes Zachariassen's claim that Drebbel stole the idea from him and his father, Zacharias Jansen, and claims that Galileo Galilei used his telescope after 1610 as a type of compound microscope. In 1624 Galileo saw Drebbel's design for a microscope in Rome and created an improved version of it to send to Federico Cesi, founder of the Accademia dei Lincei, who used it to illustrate "Apiarum", his book about bees.