Hi Gordon and mirror folk, I just thought that someone might know the oil they use to cover the mercury with so that it could be experimented with in the ceiling sundial situation in order to have a safer flat, level mirror. But thanks for the info, that is interesting. I've visited both observatories you mentioned, but far longer ago when this effort had not begun.
Edley. > Edley, > > 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 >
