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William Herschel's reflecting telescope of 40 ft (12 m) focal length, 1789 (1807). Artist: Unknown - Album alb4003310
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Sir William Herschel Great 40 foot telescope reflecting telescopes 1785 1789 Observatory House Slough England primary mirror Stock Photo - Alamy
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Astronomy: a 40-foot telescope constructed by William Herschel, in use outdoors. Coloured etching, 18--. | Wellcome Collection
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