But lenses absorbed some of the faint light, caused the colors to focus at different points, and could only be made to a certain size. The largest is the 40 inch refracting telescope at Yerkes observatory. Glass bigger than that would not be able to hold itself up! SO…
Designed by Isaac Newton – originally designed with no secondary mirror or eyepiece. You just put your eye near the top and looked in! Eyepieces and cameras made it all easier to use.
You could make a glass mirror a LOT bigger than 40 inches – and it didnt distort the light. A 5 meter mirror (the Hale telescope at Mt. Palomar) was the largest for a long time. Currently, the largest Single Piece of glass telescope is 8 meters (Subaru and others)
People were still unsatisfied – and came up with the idea of putting together a number of carefully made mirror segments, controlled by computer to stay extremely accurate. Keck I was a 10 meter segmented telescope – and the current largest. The addition of Keck II (another 10 meter telescope) makes a very large telescope array.
The deeper the curve, the closer in the focal point. Optical telescopes have farther focal points, Radio telescopes have shorter ones.
To make a shorter telescope, they put a secondary mirror in front to reflect it back through the main mirror. Most large telescopes use this design.
24 inch Schmidt at Palomar Used for taking images of solar system objects – planets and comets.
Optical Telescopes are on Mountain tops Away from the lights of the cities, above the clouds, above the weather, Radio Telescopes are in Valleys Avoiding the radio noise made by cities, cars, and radio stations X-ray and Gamma ray telescopes are in space X-rays and Gamma rays cant get through the atmosphere!
Radio Telescopes Seeing one kind of invisible light
Built by Grote Reber Now at NRAO- Greenbank First Radio Telescope *
The Big Ear - OSU (dismantled) Developed by John Kraus
Disclaimer Aloha I put together these power points for use in my science classes. You may use them in your classes. Some images are public domain, some are used under the fair-use provisions of the copyright law, some are mine. Copyright is retained by the owners! Ted Brattstrom