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".
Thermoscope
It is thought, but not certain that Galileo Galilei discovered the specific principle on which the device is based and built the first thermoscope in 1593. Galileo mentioned to his friend Cesare Marsili that he invented a thermoscope as far back as 1606. The inventor could be his physician friend Santorio Santorio or another person of the learned circle in Venice of which they were members. What is certain is that the thermoscope has started circulating in market squares during Galileo's time. The development of the actual device is attributed to four inventors namely, Galileo, Santorio Santorio, Robert Fludd, and Cornelius Drebbel. However, the general pneumatic principle of the thermoscope was used in the Hellenic period, and it was written about even earlier, by Empedocles of Agrigentum in his 460 B.C. book "On Nature".