Optical telescopes for astronomy and other imaging applications have been steadily increasing in size. Although a generation of 3–5m telescopes was constructed from 1940 to 1980, a large number of even smaller telescopes was still being built or in operation. Figure 1.1 is a logarithmic plot of telescope primary mirror diameters versus construction year for a representative selection of telescopes, beginning with Galileo’s first telescope from 1609. To a reasonable approximation, the plots of the diameters lie on a straight line, indicating a constant doubling time over the years. On average, telescope diameters have doubled over 60 years. However, since the middle of the 20th century, telescope diameters have grown more rapidly with a doubling time of about 16 years.
KeywordsRadio Telescope Large Telescope Optical Telescope Small Telescope Telescope Diameter
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