History of the telescope a wider field of view than a classic Cassegrain. During the period 1850–1900, reflectors suffered from problems with speculum metal mirrors, and a considerable number of "Great Refractors" were built from 60 cm to 1 metre aperture, culminating in the Yerkes Observatory refractor in 1897; however, starting from the early 1900s a series of ever-larger reflectors with glass mirrors were built, including the Mount Wilson 60-inch (1.5 metre), the 100-inch (2.5 metre) Hooker Telescope (1917) and the 200-inch (5 metre) Hale telescope (1948); essentially all major research telescopes since 1900 have been reflectors. A number of 4-metre class (160 inch)
WorldWide Telescope The WorldWide Telescope program makes use of IVOA standards for inter-operating with data providers to provide its image, search and catalog data. Rather than concentrate all data into one database, the WorldWide Telescope sources its data from all over the web and the available content grows as more VO compliant data sources are placed on the web. The WorldWide Telescope Windows client application supports both single and multichannel full-dome video projection allowing it to power full dome digital planetarium systems. It is currently installed in several world-class planetariums where it runs on turn-key planetarium system. It can also be used