Liquid-mirror telescope has quality cost
Advantages and disadvantages
The greatest advantage of a liquid mirror is its small cost, about 1% of a conventional telescope mirror. This cuts down the cost of the entire telescope at least 95%. The University of British Columbia’s 6-meter Large Zenith Telescope cost about a fiftieth as much as a conventional telescope with a glass mirror.
The greatest disadvantage is that the mirror can only be pointed straight up. Research is underway to develop telescopes that can be tilted, but currently if a liquid mirror were to tilt out of the zenith, it would lose its shape. Therefore, the mirror's view changes as the Earth rotates, and objects cannot be physically tracked. An object can be briefly electronically tracked while in the field of view by shifting electrons across the CCD at the same speed as the image moves; this tactic is called time delay and integration or drift scanning. Some types of astronomical research are unaffected by these limitations, such as long-term sky surveys and supernova searches. Since the universe is believed to be isotropic and homogeneous (this is called the cosmological principle), the investigation of its structure by cosmologists can also use telescopes highly reduced in their direction of view.
Since mercury metal and its vapor are both toxic to humans and animals, there remains a problem for its use in any telescope where it may affect its users and others in its area. In the Large Zenith Telescope, the mercury mirror and the human operators are housed in separately ventilated rooms. At its location in the Canadian mountains, the ambient temperature is fairly low, which reduces the rate of evaporation of the mercury. The less toxic metal gallium may be used instead of mercury, but it has the disadvantage of high cost. Recently Canadian researchers have proposed the substitution of magnetically deformable liquid mirrors composed of a suspension of iron and silver nanoparticles in ethylene glycol. In addition to low toxicity and relatively low cost, such a mirror would have the advantage of being easily and rapidly deformable using variations of magnetic field strength.
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