A look at the Biggest Telescopes in the World

A look at the Biggest Telescopes in the World


Title: A look at the Biggest Telescopes in the World

Author: Will Kalif

Article:
The Telescope turns 400 years old this year and in four century
period astronomers and telescope makers have been continually
making larger and larger telescopes in order to peer deeper and
deeper into the mysteries of the universe. There are currently
quite a few enormous instruments in use and there are several
next generation telescopes being developed that will dwarf
anything currently in use. This article takes a look at some of
these magnificent monsters of astronomy.

The largest Refractor telescope

Refractor telescopes are renowned for their absolute sharpness
of image because they are composed of very large lenses of
compounds of glass which gives them crystal clear images. But
they are extraordinarily difficult to make in a large size.
Their own weight distorts their shape and makes them unusable
above a certain size.

The largest refractor in the world is the Yerkes telescope which
has a primary lens that is 40 inches in diameter. It was
completed in 1897 and was built by the famous master optician
Alvan Clark. It represents the pinnacle of refractor telescope
making and no larger one has since been built in the hundred
years since. Reflectors are much more feasible for larger sizes
and there are many of this type that are extraordinarily large.
It is with reflectors that we achieve very large instruments.

The Big Reflectors

Reflector telescopes come in two different types. The first type
is the single mirror type where a single piece of glass is cast
and polished to make the primary mirror. The second type is the
segmented mirror where a series of hexagonal mirrors are
assembled together into a single large mirror. This type of
mirror looks much like the honeycomb from a beehive and this new
technology is allowing telescope makers to make instruments
larger than ever imagined.

The largest single piece of glass telescope in the world is the
Large Binocular Telescope (LBT) in Arizona. It is a telescope
composed of two separate mirrors that are side by side and work
in tandem. The light from both of them are blended into one
single image. Each mirror is 8.4 meters (330 inches) in width
and when used together they create the equivalent of a mirror
that is 11.8 meters (464 inches) across which is currently the
largest light collecting size on Earth. It is located in Mount
Graham International Observatory in Arizona.

Segmented mirrors pose technology challenges that have been
overcome in the past decade and now these multiple mirror scopes
are being built in extremely large sizes that cannot be rivaled
by single piece mirrors. Of the segmented telescopes where a
series of honeycomb shapes are assembled together into a single
telescope there are three different observatories with these
largest of mirrors.

The South African Large Telescope (SALT) is the largest primary
mirror scope in the world and it has a segmented mirror that is
11 meters (433 inches) across.The Big Reflectors

Reflector telescopes come in two different types. The first type
is the single mirror type where a single piece of glass is cast
and polished to make the primary mirror. The second type is the
segmented mirror where a series of hexagonal mirrors are
assembled together into a single large mirror. This type of
mirror looks much like the honeycomb from a beehive and this new
technology is allowing telescope makers to make instruments
larger than ever imagined.

The largest single piece of glass telescope in the world is the
Large Binocular Telescope (LBT) in Arizona. It is a telescope
composed of two separate mirrors that are side by side and work
in tandem. The light from both of them are blended into one
single image. Each mirror is 8.4 meters (330 inches) in width
and when used together they create the equivalent of a mirror
that is 11.8 meters (464 inches) across which is currently the
largest light collecting size on Earth. It is located in Mount
Graham International Observatory in Arizona.

Segmented mirrors pose technology challenges that have been
overcome in the past decade and now these multiple mirror scopes
are being built in extremely large sizes that cannot be rivaled
by single piece mirrors. Of the segmented telescopes where a
series of honeycomb shapes are assembled together into a single
telescope there are three different observatories with these
largest of mirrors.

The South African Large Telescope (SALT) is the largest primary
mirror scope in the world and it has a segmented mirror that is
11 meters (433 inches) across.

The Gran Telescopio Canarias or GTC is located on the island of
LaPalma Spain and it has a segmented primary mirror that is 10.4
meters in diameter (409 inches) which makes it the single
largest mirror in the world.

The Keck Telescopes are a pair of telescopes located at the Keck
Observatory in Hawaii. Each mirror is ten meters (400 inches) in
diameter.

Bigger Telescopes to come

There are even larger telescopes currently in the proposal,
development, or construction stage. Technology improvements over
the past decade have made a new scale of telescope possible and
this new scale is referred to as ELT or Extremely Large
Telescopes and it is the next generation to come. ELT's are
telescopes that are more than twenty meters in diameter which is
double the size of existing telescopes. And this doubling of
size gives significantly more than double the light gathering
power. Most of these scopes will be of the segmented mirror type
but one notable exception is the Giant Magellan telescope which
will be composed of seven spherical mirrors constructed together
so they act as a single mirror. This project is scheduled for
completion in 2016. It will be located in Las Companas
Observatory, Chile

The Thirty Meter Telescope (TMT), which is currently in
development, will be thirty meters across and composed of
segmented mirrors. It is expected to be a telescope of unmatched
performance and is predicted to be able to image planets
circling other stars. The current time line for this project is
for it to be completed somewhere around 2017 - 2018.

What about the Famous Hubble Telescope? The primary mirror in
the Hubble is 2.4 meters across (94.5 inches) which makes it
rather small compared to some of the giants listed in this
article. So then why is it the most spectacular telescope ever
created? The big advantage the Hubble has over all the other
telescopes is that it doesn't have to peer through the soup of
Earth's atmosphere. And this advantage is staggering. That is
why the Hubble has brought us some of the most extraordinary
images ever recorded.

What comes after the Hubble?

NASA is currently working on its next generation space
telescope. It is called the James Webb Space Telescope (JWST).
The primary mirror will be 6.5 meters (21.3 feet) in diameter.
Launch is planned for 2013.

Since the invention of the first telescope 400 years ago man has
been building ever larger telescopes. The telescopes to come
will bring us images of planets around other stars and who
knows, they may bring us images of the very birth of the
universe we live in.

About the author:
To learn more about the amazing world of telescopes visit the
author's website : The
Telescope Nerd