Galileo demonstrates one of his telescopes to the ruler of Venice in August 1609 (Galileo is standing to the right of the telescope)
(Image: Science Photo Library: from <a href="http://eu.wiley.com/WileyCDA/WileyTitle/productCd-3527408657.html"><i>Eyes on the Skies: 400 Years of Telescopic Discovery</i></a> by Govert Schilling and Lars Lindberg Christensen)
In celebration of the International Year of Astronomy in 2009, Â鶹´«Ã½ takes you on an armchair tour of some of the most important telescopes ever built.
