Large Zenith Telescope
The Large Zenith Telescope (LZT) was a 6.0-meter diameter liquid-mirror telescope located in the University of British Columbia's Malcolm Knapp Research Forest, about east from Vancouver, British Columbia, Canada (north from Maple Ridge). It was one of the largest optical telescopes in the world, but still quite inexpensive. The telescope was completed in the spring of 2003 and decommissioned in 2016. Design While a zenith telescope has the disadvantage of not being able to look anywhere but at a small spot straight up, its simplified setup permits the use of a mirror consisting of a smoothly spinning pan filled with liquid mercury. Such a mirror can be made much larger than a conventional mirror, greatly increasing light collecting ability. The LZT is used for ''transit imaging'', meaning that Earth's rotation moves stars along the sensor, and the latent image in the sensor is moved electronically in step with this movement, so that it is read out at the trailing edge. The ...
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Liquid-mirror Telescope
Liquid-mirror telescopes are telescopes with mirrors made with a reflective liquid. The most common liquid used is mercury, but other liquids will work as well (for example, low-melting alloys of gallium). The liquid and its container are rotated at a constant speed around a vertical axis, which causes the surface of the liquid to assume a paraboloidal shape. This parabolic reflector can serve as the primary mirror of a reflecting telescope. The rotating liquid assumes the same surface shape regardless of the container's shape; to reduce the amount of liquid metal needed, and thus weight, a rotating mercury mirror uses a container that is as close to the necessary parabolic shape as possible. Liquid mirrors can be a low-cost alternative to conventional large telescopes. Compared to a solid glass mirror that must be cast, ground, and polished, a rotating liquid-metal mirror is much less expensive to manufacture. Isaac Newton noted that the free surface of a rotating liquid forms a ...
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