From NCERTAsked by Anonymous from Dallas, United States24 Oct 2026, 5:59 AM ISTUpdated
In one line
Telescopes are placed on mountains to get a clearer view of space by avoiding dust, pollution, and city lights.
Indian Astronomical Observatory — Astronomy station in Hanle, India The Indian Astronomical Observatory in Hanle, Ladakh, built on a high mountain for clearer views of space. Image: Wikipedia
The rule
Telescopes work best where the air is clean, dry, and there is less light from cities, so they are often built on high mountains.
Let's understand it simply
Imagine you are trying to look at stars from your house in a big city. The sky looks dull because of street lights, car smoke, and clouds. Now, think about going to a hill station like Ooty or Ladakh. The sky looks much clearer, and you can see many more stars. This is because there is less pollution and fewer lights. Telescopes work the same way. They see better when the air is clean and dark, which is why scientists put them on mountains.
How it works
At higher places, the air is thinner and cleaner, so less dust and pollution block the view.
Mountains are far from city lights, so the sky is darker, making faint stars easier to see.
There is less water vapor (moisture) in the air, which means clearer pictures.
The telescope can collect more light from space without interference.
Why telescopes are placed on mountains
Less air pollution and dust
Fewer city lights (darker sky)
Less water vapor (clearer images)
Closer to space (thinner atmosphere)
The story behind it
Long ago, astronomers noticed that their telescopes worked better on clear nights and in places far from cities. As science grew, they started building observatories (special buildings for telescopes) on mountains. For example, the Indian Astronomical Observatory is in Hanle, Ladakh, one of the world's highest sites.
Where you see it in real life
Hanle Observatory in Ladakh: Built high up to get clear views of stars.
Kodaikanal Observatory: On a hill to avoid city lights and dust.
Mauna Kea in Hawaii: One of the best places for telescopes because of its height and clear sky.
Astronomers camping on hills: Even small telescopes show more stars from a mountain than from a city.
Why it matters
Helps scientists discover new planets, stars, and galaxies.
Gives us better pictures and information about space.
Used for weather prediction by watching space objects.
Important for students and researchers in astronomy.
Common mistakes
Thinking telescopes are only for looking at stars (they also study planets, galaxies, comets).
Believing any high place is good (it must also be dry and away from lights).
Remember it
"Higher, darker, cleaner — better for telescopes!"
Check yourself
Why do telescopes on mountains see more stars than those in cities?
Because there is less pollution and fewer city lights blocking the view.
What is one main reason telescopes are not placed in crowded cities?
City lights make the sky too bright, so faint stars cannot be seen clearly.
How does less water vapor help telescopes?
It makes the air clearer, so telescopes get sharper images of space.
Why is Hanle in Ladakh a good place for a telescope?
It is high, dry, and far from city lights, so the sky is very clear.
Quick recap
Mountains have less dust and pollution, so telescopes see better.
Being far from city lights makes the sky darker for clearer images.
Less water vapor at high altitudes means sharper pictures.
Many famous observatories are built on mountains for these reasons.
