Experiments with rotating mercury mirrors go back many decades. It takes a very constant speed drive to keep the focal length constant. The casting of large glass telescope mirror blanks at the University of Arizona includes rotating the oven so that the molten glass acquires a parabolic shape.
Several large telescopes have been floated on mercury, for example, the 100-inch Hooker reflector on Mount Wilson, CA, and the 250-ton Dunn solar tower telescope on Sacramento Peak, NM.
http://www.sunspot.noao.edu/DSTWWW/vttpr.html Gordon At 04:57 PM 1/5/02 -0800, Edley McKnight wrote:
Hi John and all, John wrote: In an astronomy paper I read last year from an observatory in the southern hemisphere there was an article on a large parabolic mercury mirror obtained by rotation. The key points in the article were the need to prevent fumes from the mercury, damp vibration, prevent oxidation and eliminate the meniscus at the edges. They had found a synthetic oil or oil/polymer mix that damped the vibration, sealed the surface, with the mercury and the enclosure had no meniscus and prevented oxidation. Something like this, further sealed to prevent dust, would allow the mercury surface itself to be used as the mirror. ( I'm assuming from it's use as an astronomical mirror that the refractive effects of the liquid are minimal ) Edley McKnight [43.126N 123.357W]
Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
