Overwhelmingly Large Telescope
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The Overwhelmingly Large Telescope was a conceptual design by the European Southern Observatory organization for an extremely large telescope, which was intended to have a single aperture of 100 meters in diameter. Wikipedia
Diameter: 60, 100 m (196 ft 10 in, 328 ft 1 in)
Focal length: 175 m (574 ft 2 in)