Large Zenith Telescope, Liquid-mirror telescope in Malcolm Knapp Research Forest, British Columbia, Canada

The Large Zenith Telescope was a 6.0-meter liquid-mirror telescope in the University of British Columbia's Malcolm Knapp Research Forest, about 70 km east of Vancouver. Its primary mirror was a spinning pan of liquid mercury, guided by an air bearing and driven by a brushless motor, forming a parabola under centrifugal force. A thin Mylar film covered the mercury, and corrector optics sat above it in the primary focus.

The Large Zenith Telescope was completed in spring 2003 at the University of British Columbia's Malcolm Knapp Research Forest, 70 km east of Vancouver, and scientific work ran from 2004 until dismantling in 2016. It reused parts of NASA's 3-meter Orbital Debris Observatory liquid-mirror telescope. Its 6-meter mercury mirror was built as a test for about $1 million.

The LZT was built for transit imaging: Earth's rotation sweeps stars across the sensor, and the latent image is shifted electronically in step so it is read out at the trailing edge. Its corrected field covered 24 arcminutes, the camera 17, allowing exposures of up to 7 arcminutes before stars drifted off. The site sits at 395 m in the Malcolm Knapp Research Forest, north of Maple Ridge.

The telescope was decommissioned in 2016, so there is no working observatory to tour. It stood in the Malcolm Knapp Research Forest of the University of British Columbia, about 70 km east of Vancouver and north of Maple Ridge, at an elevation of 395 m. Access to the research forest is controlled by the university, so check conditions before travelling.

The mirror was a 6.0-metre pan of liquid mercury, spun on an air bearing with a brushless electric motor built into it; an optical encoder and control loop held the rotation constant. A thin Mylar film covered the mercury to keep air currents off the surface. The completed mirror was reported to have cost about $1 million, roughly 1% of a conventional mirror of the same size.