Why Are Observatories Built On Mountain Tops?

The universe has been studied for centuries to understand its origins and composition.

To do this, astronomers have used observatories, thus, making stars more visible for them.

Most of them tend to be in the mountains, probably to have a better look. The article below will explore their reasons further.

What are Observatories?

This question might seem a no-brainer, but it is important to know what an observatory is before delving into the reason why they’re located in mountaintops. 

Alongside Institutes and Centers with astronomical facilities, they maximize scientific findings when it comes to exploring the night sky. 

Now, observatories are more than just an ensemble of telescopes. They’re able to find what astronomers wouldn’t be able to without equipment.

Observatories’ classification is based on the part of the electromagnetic spectrum that they’re capable to observe. 

Most of them are optical, which means that they’re designed to spot celestial beings that are visible to the human eye. 

However, some observatories can detect radio waves and satellites that carry telescopes and detectors. 

These are equipped to study celestial sources of gamma rays and x-rays from above the atmosphere.

History Behind Observatories

Astronomical observatories have been around for centuries. 

Their predecessors were monolithic structures that tracked the positions of the Sun and Moon. The first civilizations did this to keep track of the time. 

The most famous example is Stonehenge, which was built in England around 3000 to 1520 BCE. 

Babylonians didn’t fall behind, observing celestial movements from terraced towers called ziggurats.

Mayans were also known to use celestial beings for timekeeping. 

The dome-shaped structure at “El Caracol” (The Snail) in the Yucatán Peninsula, Mexico, is clear proof of them catching up to the Babylonians. 

Interestingly enough, its structure resembles a modern optical observatory, but there’s no evidence of them using any other instruments. 

However, this didn’t mean that there weren’t any civilizations that did this, but more on that later.

The first observatory that used rudimentary equipment was located on the island of Rhodes, built around 150 BCE. 

Hipparchus was responsible for its creation and one of the greatest pre-Christian astronomers. 

There, he developed a magnitude system that indicates the brightness of celestial beings as well as discovering precession. 

On the other hand, there were observatories built at Damascus, Maragheh, and Baghdad around the 9th-10th century CE.

The most productive in the East was is located at Samarkand, erected by prince Ulugh Beg in 1420 CE. 

Alongside his assistants, they made a catalog of stars that came from observations with a large quadrant. 

All of this was on the Islamic side of the world.

As for Europe, their people were picking up the pace thanks to King Frederick II of Denmark.

Who built the first premodern observatory at Uraniborg, on the island of Hven, for Tycho Brahe in 1576 CE.

World’s Best Observatories

Research suggests that the best observatory in the world is the Paranal Observatory. It’s located in Chile and it’s operated by the European Southern Observatory. 

The telescope in this major hotspot for science is comprised of the telescopes Kueyen (Moon), Antu (Sun), Melipal (Southern Cross) and Yepun (Venus). 

Together, they create an interferometer that allows astronomers to see details 25 times finer than with individual telescopes.

The second best observatory is located in Chile as well, at the top of the mountain “La Silla” (The Chair)

It has an altitude of 8000 feet above the level of the sea. 

It is also operated by the ESO and it’s one of the best places for stargazing since the area is completely out of light pollution’s reach. 

La Silla Observatory is also the proud owner of the High Accuracy Radial Velocity Planet Searcher, which astronomers use for extrasolar planets.

Discoveries with ESO telescopes

One of the major discoveries by using an ESO telescope were the stars orbiting the Milky Way black hole. 

During a 26-year long study of its surroundings, the observations made with the Very Large Telescope (VLT) revealed the effects predicted by Einstein’s relativity on the motion of a star passing through the center. 

Another great discovery revolves around how the universe accelerates, which was based on observations of exploding stars at La Silla and Paranal. 

The results showed that the universe’s expansion is increasing at a fast pace.

Another great thing discovered by an ESO telescope was a planet. It was found in a habitable zone close to Proxima Centauri. 

The new planet was named Proxima b and its temperature was suitable for liquid water on its surface.

Why Are Observatories Built On Mountain Tops?

There are many reasons as to why most observatories are located in mountain tops. One of them is the distortion of starlight. 

In the thin atmosphere of the mountain tops, it can be spotted, unlike what would happen if the observatory was located elsewhere. 

Another thing is the altitude since the higher it is, the less atmosphere can absorb infrared energies.

Infrared energy reveals details about the coldest objects in the universe. 

Observatories that are located at the top of a mountain can easily spot clouds of gas and dust and the disks that give birth to planets. 

If the atmosphere absorbs all the infrared energy, this could mean that astronomers’ labor of finding them will be harder. 

On the other hand, mountaintops have unobstructed views of the horizon in all directions. 

This allows them to explore the night sky without being disturbed by the light pollution that accompanies cities and towns since most of them are located in plains and valleys.


An observatory is an ensemble of telescopes that make exploring the night sky easier for astronomers

Since they’re able to find what would normally be invisible for the naked eye. 

They have been around for centuries, evolving from monolithic structures.

That was used to keep track of the time to a very sophisticated telescope that can spot celestial beings and detect radio waves. 

The best observatories are located in Chile, with telescopes operated by the European Southern Observatory (ESO)

Which discovered stars in Milky Way’s black hole. 

Now, the reason why observatories are at mountaintops is to avoid light pollution.