Is the Worlds largest telescope refracting or reflecting?

Answer 1

Large lenses deform under their own weight, but mirrors can be supported. Reflectors do not suffer from chromatic aberration like refractors do. Large mirrors need only one optical surface, achromats four surfaces to grind.

Large, very clear lenses are harder to cast than more tolerant mirror blanks.

Answer 2

The engineering required to build a very large refracting telescope would be many times more expensive than an equivalent reflector. With the mirror optics of a reflecting telescope, the telescope can be "folded" so that light passes through the barrel of the telescope three or more times, while a refracting telescope is straight.

Another reason even more important, is that in a refracting telescope the light passes THROUGH the glass lenses, while in a reflector the light bounces off a polished mirror. When light passes through a glass lens, some little bit of the light is absorbed and lost; in a reflector, everything bounces off.

To make this even worse, the lenses for a large diameter refracting telescope would have to be quite thick even at the edges to support their own weight, and the amount of light lost depends on the thickness of the lens.

So reflecting telescopes not only handle the light more efficiently, but are easier to build.
Due to the larger weight involved with a larger telescope, a lens in a large refracting telescope will become distorted and no longer project an image to the proper focal point. With a reflecting telescope, this problem is not as prominent and if it does happen it does not have as big of an impact on the image.

Answer 3

I would qualify that as "most LARGE telescopes". Telescopes for home use can be of both types. (1) For a large telescope, there is a limit to how large the main lens can be before it collapses under its own weight. A mirror, on the other hand, can be supported on its bottom side - and it need not be as thick as the corresponding lens. (2) In a lens, two sides must be polished. In a mirror, only one. (3) A mirror doesn't have the problem of chromatic aberration - that is, different colors of light being refracted differently, in a lens telescope.

Answer 4

In any question which includes "the largest", the answer must include the phrase "so far".

As of May 2010, the largest optical telescope SO FAR is the "Gran Telescopio Canarias", or "Great Canary Islands Telescope" in the Canary Islands, Spain.

Answer 5

No. The world's largest telescopes are reflecting. A prism breaks white light into a number of colors. High quality cameras have lenses made of four elements. They make the light of various colors focus on the same place. The largest refracting telescope is 36 inches across. A lens of four elements can only see colors in the visible spectrum. It can not see ultraviolet or infrared. A larger refracting telescope would be too heavy for machinery to support.

Answer 6

The largest refracting telescope has a diameter of 1 meter and is located in William's Bay, Wisconsin.

the largest refracting telescope in the world, at the Yerkes Obsercatory in Williams Bay, Wisconsin, has a diameter of only 1 m.

Answer 7

Reflecting telescopes give a brighter, clearer image that refraactors in many cases. Add to that the fact that refractors become very impractical with objective lens sizes much above 40 inches, while reflectors can have mirrors of 200 inches and more.

Answer 8

Because large refractors mean large lenses, which are incredibly difficult to make. It's hard enough to make large mirrors, which is why the largest telescopes now use multiple smaller mirrors instead of one big one.

Answer 9

Mirrors have various advantages over lenses:

1. only one surface needs to be polished
2. they can be supported on the underside
3. less light is absorbed
4. they don't suffer from "chromatic aberration"

A 200-inch mirror is difficult to make, but a 200-inch lens with a focal length short enough to be useful would be impossible to make; if it were thin at the edge it would break from its own weight, and if the edges were thick enough not to break it would absorb so much light as to be useless.

Answer 10

Most large modern telescopes are reflectors, because a large refracting telescope is enormous and heavy. The primary telescope of the Lick Observatory near San Jose, California may be the largest refracting telescope.