<p> 6 th Grade Science Notes February 25, 2010 Optical telescopes:</p><p> Telescopes collect and focus different types of electromagnetic radiation, including visible light.  Optical telescopes use either mirrors or lenses to collect and focus visible light. There are 2 kinds of optical telescopes: refracting and reflecting telescopes.  Galileo made the first refracting telescope with 2 glass, convex lenses. A convex lens is thicker in the middle than at the edges.  Isaac Newton made the first reflecting telescope using concave and flat mirrors to focus visible light. The larger the curved mirror, the more light it can collect and focus. All the large, optical telescope today are reflecting telescopes.  The Keck Observatory has the world’s 3 largest reflecting telescopes on the top of Mauna Kea in Hawaii. Mountain observatories can avoid the problem of air and light pollution and atmospheric distortions that can affect their views of space.  The Hubble Space Telescope is a reflecting telescope in orbit above the earth’s atmosphere so its images are amazingly clear. It also collects other types of EM radiation. (UV, IR, VL)</p><p>Other telescopes:</p><p> Telescopes today may collect infrared, ultra-violet, x-ray and gamma ray radiation from space. Some need to be in orbit because the earth’s atmosphere blocks many of these wavelengths of the electromagnetic spectrum.  The Arecibo Radio Telescope in Puerto Rico is largest radio telescope in the world. Radio waves have very long wavelengths and so need a very large collection dish. Radio astronomy has shown us images from the edge of the universe because radio waves can travel very long distances.  The Chandra telescope is in orbit and collect x-rays given off by black holes, supernova and quasars that are at the edge of the universe.  The Spitzer Space Telescope was launched into orbit in 2003 and collects infrared light.  SOHO (Solar Heliospheric Observatory) is in orbit and collects all types of electromagnetic radiation from our closest star – the sun. </p><p>Cool sites to go to: http://www.spitzer.caltech.edu/ http://sohowww.nascom.nasa.gov/ http://hubblesite.org/ http://chandra.harvard.edu/</p>