I could be wrong (always a fair chance!) but I don't think Galileo is generally credited with inventing the telescope. He may have improved on the other designs of the time (invented by Hans Lippershey or somebody else <
http://en.wikipedia.org/wiki/Hans_Lippershey>) but his main claim to fame is that he turned hs scope towards the heavens at night and published records of what he saw (the last bit is important). Galileo's observations of the Galilean moons orbiting Jupiter (i.e., proof that not everything in the heavens revolved around the Earth) was a very big deal and along with his other writings got him into a mite of trouble with the church.
