{{Short description|Decommissioned liquid mirror telescope in British Columbia}} {{Infobox 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 {{convert|70|km|0|abbr=on}} east from [[Vancouver]], British Columbia, Canada (north from [[Maple Ridge, British Columbia|Maple Ridge]]). It was one of the [[List of largest optical reflecting telescopes|largest optical telescopes]] in the world, but still quite inexpensive. The telescope was completed in the spring of 2003 and decommissioned in 2016.
== Design == [[File:Comparison optical telescope primary mirrors.svg|thumb|left|Comparison of nominal sizes of primary mirrors of the Large Zenith Telescope and some notable optical telescopes]] 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 (element)|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 telescope made use of parts from the 3-meter diameter [[NASA Orbital Debris Observatory]] telescope, which had been using a liquid-mercury mirror for several years.
This mirror was a test, built for $1 million, but it was not suitable for astronomy because of the test site's weather. In 2016 it was noted as the third largest telescope in North America, and for its spinning mercury mirror that cost just 1% of normal mirrors, although it must view upward.<ref>{{Cite web|date=2016-05-06|title=World's Largest Liquid Mirror: Large Zenith Telescope|url=https://interestingengineering.com/largest-liquid-mirror-telescope-earth-large-zenith|access-date=2019-10-09|website=interestingengineering.com|language=en-US}}</ref>
== Decommissioning == According to ''[[Atlas Obscura]]'' the Large Zenith Telescope was decommissioned in the summer of 2016.<ref>{{cite web|url=https://www.atlasobscura.com/places/large-zenith-telescope|title=Large Zenith Telescope|website=Atlas Obscura|access-date=November 17, 2021}}.</ref> All of its liquid [[Mercury (element)|mercury]] was stored for other projects.{{citation needed|date=February 2018}}
The website ''Physics Footnotes'' also mentioned that the LMT had been decommissioned, but gave no time frame in the undated article.<ref>[https://physicsfootnotes.com/footnotes/liquid-mirror-telescopes/ Physics Footnotes: Liquid Mirror Telescopes].</ref>
''[[Science (journal)|Science]]'' magazine reported in 2019 that the LMT was decommissioned, but was also silent on the date.<ref>{{Cite web|last=Clery|first=Daniel|date=2019-07-18|title=Could humanity's return to the moon spark a new age of lunar telescopes?|url=https://www.science.org/content/article/could-humanity-s-return-moon-spark-new-age-lunar-telescopes|access-date=2019-10-09|website=Science – AAAS|language=en}}</ref>
== Similar projects == The university plans a larger 8-meter liquid-mirror telescope named the Advanced Liquid-Mirror Probe (ALPACA) for astronomical use at an estimated first-light cost of $5 million, $3 million contingency, $10 million for the camera, $5 million for a [[Optical spectrometer|spectrograph]], and $0.3 million operating costs per year.<ref>[http://user.astro.columbia.edu/~arlin/arcscopes.pdf ALPACA overview].</ref>
A larger project is planned, called LAMA, with 66 individual 6.15-meter telescopes with a total collecting power equal to a 55-meter telescope, resolving power of a 70-meter scope.<ref>Hickson, P. and Lanzetta, K. M., 2004, July. [https://www.researchgate.net/publication/228720624_Large_Aperture_Mirror_Array_LAMA_-_project_overview Large aperture mirror array (LAMA): project overview]. In Second Backaskog Workshop on Extremely Large Telescopes (Vol. 5382, pp. 115–126). International Society for Optics and Photonics.</ref><ref>[http://astro-canada.ca/l_observatoire_a_miroir_liquide_de_l_universite_de_la_colombie_britannique-the_university_of_british_columbia_liquid_mirror_observatory-eng The University of British-Columbia Liquid-Mirror Observatory - Perfecting the next generation of super telescopes].</ref>
== See also == * [[List of largest optical reflecting telescopes]] * [[List of the largest optical telescopes in North America]] * [[Lists of telescopes]]
== References == {{Reflist}}
== External links == * [http://www.astro.ubc.ca/LMT/ LMT web site at UBC].
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[[Category:Liquid mirror telescopes]] [[Category:Astronomical observatories in Canada]]