The
The idea of using a rotating liquid to create a perfect paraboloid was
originally proposed by Sir Isaac Newton but the very stringent
requirements, in particular on the speed of rotation and leveling,
prevented any serious attempt to build a prototype before the second
part of the nineteenth century. The first published account of a working
LMT was provided by Skey (1872), who constructed a 35cm telescope, and
made the first detailed calculations of the focal length in terms of
angular velocity.
By 1909 an optical physicist, Robert Wood, published
a series of papers describing his success using a 51cm LMT. He carefully
analyzed the main sources of vibrations, and was able to obtain photographic
trails of stars. He could even resolve double stars having separations as small
as 2.3 arcsec. In order to suppress the ripples on the
surface of the mirror, he experimented with the effect of oil layers.
In spite of his success, Wood decided to abandon the LMT because he felt
that its restriction to zenith observations made the astronomical applications
too limited.
In the picture you can see a liquid mirror telescope being tested with water, but obviously the magic doesn’t start until you fill the pool with liquid mercury. The biggest disadvantage of these systems is that you can’t turn them at all.. they are always pointing to the zenith. Luckily the earth is still revolving, so you can still get to see different parts of the sky. You can’t move these around all that easily either. And mercury vapour levels need to be monitored at all times.
A popular science magazine had instructions on how to make one of these using resin and a turntable player.
Posted by api in Wonders of technology