At the end of the 19th Century and beginning of the 20th Century, telescopes and observatories started appearing throughout the world. Many were installed by universities so they could both teach students about astronomy and to conduct research. Often times, they were installed on the university campus. As time went on and telescopes advanced, three problems occurred.
- Light pollution started to interfere with the quality of images. The world electrified, street lamps and bright signs were installed, and the price of electricity was low. There was no thought given to conservation of energy and keeping this light from flowing to where it wasn't needed, such as up into the sky.
- Astronomers realized that their imagery would improve if they could place their telescopes as far above sea level as possible. Light from distant objects were distorted less as it passed through less of the atmosphere.
- Weather would prevent telescope usage some part of the time.
Universities would move their telescopes to mountain tops to lessen these problems. That is, until mountains close to big cities also fell victim to light pollution. As astronomers wanted to peer farther into the universe, observing increasingly dim objects, minimizing light pollution and atmospheric distortions became a high priority.
In the second half of the 20th Century, many moved their telescopes to mountain tops and deserts in more ideal places, where the climate ensured visibility a high percentage of the time and there was a minimum of distortion from moisture. One of those mountains was Haleakalā in Hawaii, but local populations objected to modern technology encroaching on sacred places, so mountains in Chile were often used instead–as long as the view of the universe from Earth's southern hemisphere was acceptable. If it wasn't acceptable, mountain tops in the Canary Islands were an alternative.
When, in the 1930s, astronomers discovered that objects in the universe emitted electromagnetic energy that could be received on Earth, they built radio telescopes to receive the signals. However, man-made emissions from electrically-operated devices interfered with them, so they too were best installed in remote areas with a minimum of human activity.
These are the places in the world that now host significant numbers of telescopes that are owned and/or operated by organizations in other countries:
|Caldera de Taburiente||La Palma, Canary Islands|
|Mount Teide||Tenerife, Canary Islands|
|Cerro La Silla||Chile|
The map segment below shows the telescopes on Mount Teide on the island of Tenerife in the Canary Islands. These are nominally 2,400 meters (7,874 feet) above sea level. Of the sixteen telescopes, six are solar telescopes.
This map segment shows twenty telescopes along a ridge on Cerro La Silla, Chile. All of the telescopes are optical telescopes except one, which is a radio telescope.
This photo shows some of the radio telescope dishes on Mauna Kea on the island of Hawaii.