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Optical telescopes use lens combinations that magnify images perceived “by eye.”

In the cover image you can see the “Gran Telescopio Canarias” a 10.4 m (410 in) reflecting telescope located on the island of La Palma, in the Canaries, Spain. Credit: Wikipedia

Telescopes expand vision capabilities

Thanks to the invention of new instruments that expand the range of the senses, astronomy has managed to recover traces of the universe’s past.

Until the 20th century, only optical telescopes were used, which captured visible light.

Electromagnetic waves
Electromagnetic Waves, Electromagnetic Spectrum  Credit: web “”

Radiation from space has a very wide range of wavelengths.

Our retina is activated only by what we call “visible light.”

It is very important to know that we cannot perceive the other waves that enter through the pupil of the eye.

Advantages and difficulties of optical telescopes

Optical telescopes use lens combinations that magnify images perceived “by eye.”

But there are technical problems that prevent making lenses that have a large diameter.

To the difficulties of polishing the lens, it is added that of supporting them properly when their weight becomes very great.

Since the manufacture of the first telescopes, the convenience of using large surface mirrors was seen, which capture more light and reflect it to a focal point of observation.

Telescopes work as if our pupil were enlarged. That is why it is said that we now have “gigantic eyes open to the Universe.”

In 1668, Isaac Newton invented the reflecting telescope, the first telescope to work with mirrors. It had a diameter of 33 millimeters (0.033 meters).

Telescope Newton. Optical telescopes
A replica of Newton’s second reflecting telescope, which he presented to the Royal Society in 1672. Credit: web “”

In July 2009, there were 21 optical telescopes with a diameter greater than 4 meters, all of them built in the last 20 years.

The largest of them all is the Gran Telescopio Canarias, located on the beautiful island of La Palma and inaugurated on July 24, 2009. The Keck telescope, operating since 1993, is 9.80 meters in diameter.

Telescopio Canarias. Optical telescopes
The Gran Telescopio Canarias (GranTeCan or GTC) is a 10.4 m (410 in) reflecting telescope located on the island of La Palma, in the Canaries, Spain. Credit: web “”

The design, construction and management of the large telescopes and the astronomical observatories that house them is of enormous cost:

The Gran Telescopio de Canarias (GTC) had an initial budget of around 120 million euros.

The Large Millimeter Telescope initially cost $ 100 million.

The SPM-Twin project, which consists of two telescopes of 6.50 m in diameter, one with a wide field and the other for infrared, involves an investment of 150 million dollars.

The Thirty Meter Telescope, which could be installed in San Pedro Mártir, in the State of Baja California in Mexico, requires close to 1,000 million dollars.

San Pedro
One of the telescopes in San Pedro Mártir, Mexico Credit: web “”

No private or state company could alone bear these “astronomical” costs.

That is why the projects are carried out through large international consortiums, where the different members make various contributions such as the development of the site and its facilities, the instruments, the mirrors, the development and operation costs, etc.

These contributions revert to industrial, scientific and educational investments of the members.

The choice of location for modern telescopes, especially those that detect radio frequency signals, is based on many well-justified scientific reasons, particularly the dryness and altitude of the site.

If the atmosphere around the telescope contained water, the waves would be largely absorbed, as the tiny drops of water would scatter them and thus degrade the quality of the observations.

The higher the altitude at which the telescope is located, the lower the density of the surrounding atmosphere and, therefore, the lower the refraction and absorption of the received waves.

Another important factor to consider is the absence of city lights.

Gemini North. Optical telescopes
Gemini North telescope dome on the summit of Mauna Kea, Hawaii.  Credit: web “”

Extremely large telescopes

Extremely large telescopes are considered worldwide to be one of the highest priorities in ground-based astronomy.

They will vastly advance astrophysical knowledge, allowing detailed studies of subjects including planets around other stars, the first objects in the Universe, supermassive black holes, and the nature and distribution of the dark matter and dark energy which dominate the Universe.

Since 2005 ESO has been working with its community and industry to develop an extremely large optical/infrared telescope.

ELT optical telescopes

Named the ELT — for Extremely Large Telescope — this revolutionary new ground-based telescope concept will have a 39-metre main mirror and will be the largest optical/near-infrared telescope in the world: “the world’s biggest eye on the sky”.

ELT. Optical telescopes
Artist impression of Telescope Extremely Large (ELT) Credit: web “”

In 2011, the governing bodies of the European Southern Observatory (ESO) have just approved their budget for next year at a meeting in Munich (Germany).

This budget already includes the preparatory work to locate the Telescope Extremely Large (E-ELT), the largest to be built on Earth, on Cerro Amazones, in Chile.

The development of some of the optical components that have already been designed. Among them a mirror 40 meters in diameter.