Hi John and all,
John wrote: > Since I don't think traditional tools like a level or inclinometer can > precisely align or measure the tilt of such a tiny mirror, perhaps the > best alignment tool is the Optical Lever Effect (OLE) itself. > > But I can think of a simple but very precise way to level a tiny mirror so > that it is perfectly horizontal... > > You could float the mirror inside a cup containing liquid mercury. You'd > make the cup slightly larger in diameter than the mirror, but not so large > that it could float too far. For my size room, I'd use a round 1 cm. > mirror and a round 1.2 cm. cup and I'd hermetically cover and seal the cup > with a thin piece of glass. The whole thing would then be securely mounted > to the outside structure of the house (maybe a steel rod?) This is the > only sure way I can think of to perfectly level a mirror. 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 ) There is also a synthetic liquid that compass cards used to be floated on which would provide a surface to float the mirror on which might be minimally toxic. Vibration could be a severe problem in some areas. The heating and cooling due to being close to a window should probably be included in any liquid aided solution. A fluid with some negative meniscus might even be an advantage, tending to center the mirror. Having fun in the rain in Oregon! Edley McKnight [43.126N 123.357W]
