How Do Telescopes Work?

by Carson

Telescopes are magnifiers that help you see distant objects clearly, and they work thanks to the specialties of light. You have probably seen one before, from an amateur one for stargazing to something as delicate as the Hubble Space Telescope. How do telescopes work? Let’s find out in this article.

What is a Telescope?

A telescope is a light collection system that helps observers resolve objects more efficiently. The more light it collects, the more details can be seen from the image. For instance, a telescope with a diameter of 1 meter is more sensitive than one with a diameter of just 10 centimeters.

Then, they bring the light into a focus, and the observer is now ready to see the results. In the following sections, we will discuss how telescopes focus light at one point for people to enjoy the view and do science.

Refracting Telescopes

Many telescopes, including the earliest ones, use lenses to refract light. When the telescope receives light from the outside world, the refractor bends light to the correct angle where all the light in the device is focused at one point. Finally, it gets to a small lens (an eyepiece), which magnifies the image so that details are readily visible. After focusing the image, the picture goes upside down because light from the left goes to the right, and vice versa.

How does refracting telescopes work?
Image Credit: NASA Space Place

Keep in mind that these lenses have to be made with incredible accuracy. If not, they will not focus light appropriately, meaning that the image will be distorted. This is what happened to the Hubble Space Telescope. It suffered from this kind of issue until a servicing mission is conducted, and “glasses” were added to correct the images. Note: The Hubble Space Telescope uses mirrors, but it can also suffer from a similar issue.

Reflecting Telescopes

Large telescopes use mirrors for observations because they are cheaper to build and can have a larger surface area, leading to more sensitivity. Famous telescopes such as the Hubble Space Telescope and the (future) James Webb Space Telescope use this method.

The light enters the telescope from the outside world, and a curved mirror is used to focus the light. At the point of focus, there is another mirror that bends the light so that it can be viewed from the observer.

How does a reflecting telescope work?
Image Credit: NASA Space Place

Unlike a two-sided lens, a mirror can have only one side and can be lighter than a lens of the same size. Therefore, it is much easier to manufacture and use less money. That’s also why space telescopes are always reflective. In fact, radio telescopes that pick up signals from spacecraft use the reflection of light and shape like large dishes.


We briefly discussed how telescopes work in this article. We covered both reflective and refractive telescopes, and made examples from simple versions. However, if we want to do science on a telescope, we need even more equipment, such as instruments and transmitters.

To learn more about telescopes, please visit the websites in the references. If any key points are missing, please let us know in the comments below.

References and Credits

  1. NASA Space Place. (2021, March 19). How Do Telescopes Work? Retrieved May 24, 2021, from
  2. (n.d.). How Telescopes Work. Retrieved May 24, 2021, from
  3. CrashCourse. (n.d.). Telescopes: Crash Course Astronomy #6. Retrieved May 24, 2021, from
  4. Avery Thompson. (2017, May 18). Watch This Cool Explanation of How Telescopes Work. Retrieved May 24, 2021, from
  5. NASA. (2019, November 25). Hubble’s Mirror Flaw. Retrieved May 24, 2021, from

Related Posts

Leave a Comment

* By using this form you agree with the storage and handling of your data by this website.