Mirror Telescopes

A mirror telescope is one that uses one or a series of mirrors to reflect a far away image so that it appears closer to the eye. They have been around for many centuries, and are still being used today.

The metal mirrors of the telescopes in the early to mid 1900s were made of tin and copper and would tarnish. Over time, they would reflect less and less light and would have to be polished. Mirror telescopes made of glass did not work well either. The light would travel through the glass and bounce off the metal backing and then back through the glass again, blurring the image.

In 1976, Russian astronomers built the biggest mirror telescope in the world. It had a 236 inch mirror and was controlled with a computer, but they could not stop the mirror from sagging under its own weight and distorting the images they were getting. To solve the problem of mirror size, they made many smaller mirrors, and with the help of a computer, they were able to synchronize them to work together as one. This was the beginning of multiple mirror telescopes.

A telescope with multiple mirrors was put on Mount Hopkins in Arizona in 1979. It had six mirrors that had a 72 inch aperture each, and they worked together to act as one larger mirror of 176 inches. In 1996, the six mirrors were removed and replaced with a 21.3 foot single mirror.

The idea of a liquid mirror telescope is an old one that was proposed by Sir Isaac Newton. The idea was to make a mirror using liquid mercury spinning at a precise speed. Just by coincidence, if you can get just the right speed, the spinning liquid will curve to just the right shape needed for a telescope mirror. The speed of the spinning motion had to be so precise that it was not possible to create until the second half of the 19th century.

With the advancement of technology, there is talk of putting a liquid mirror telescope on the moon. These mirrors would be part of an optical infrared telescope, with a 600 foot to 328 foot aperture. It could see objects 100 to 1000 times farther away than the James Webb Telescope, which is scheduled for launch in 2013.