How Telescopes Work

Maybe you are brand-new at searching for constellations or maybe you are already familiar with them. Maybe you’d just like to take in the beauty of the cosmos or maybe you’d just like to see what is taking place miles and miles away from you when a comet passes the Earth or a lunar eclipse is taking place.
Either way, you’d like to take a closer look the moon, far-off stars and planets!

With the help of a telescope you can look at stars in the night sky, admire the vastness of the universe; you can even discover new objects in the sky and new solar systems altogether! Most new space discoveries have been made my amateur astronomers watching the sky for leisure. Awesome!
A telescope is a tool used to magnify objects in the distance, whether if you use it to observe the sky or distant happenings on the ground below.
Telescopes come in many sizes and there are a variety to choose from. The question is: “which one is most suitable for you and what you should consider purchasing one? To make a more informed decision you need to have a basic understanding on how they work!

You may be aware that telescopes are represented by small-sized plastic science toys you can buy at a department store like Wal-Mart, amateur telescopes, sophisticated observatory telescopes as well as a huge state-of-the-art multi-million Dollar tool used for NASA’s scientific research we all have heard about – the Hubble Space Telescope!
There are two common types of telescopes available today; one is the refractor telescope, which uses glass lenses and the other one is the reflector telescope, which uses mirrors instead of the lenses.
They work quite differently from each other, but accomplish pretty much the same thing.

In my quest of understanding how a telescope works, I asked myself:” But how come that a comparably small 6-inch telescope allows you to decipher the writing on a tiny stamp from some 50 yards away when my naked eye can hardly see the stamp itself?”
I finally found my answer after quite a bit of Internet research:
Evidently, the part of the eye we call retina is responsible for collecting light and works like a screen upon which an image is being projected. It allows us to recognize details of an object from far away. But the reason why is it not able to collect enough light to read the writing on a stamp from 50 yards away is the fact that our retina is simply not BIG enough to do the trick by itself!

A telescope, however, helps the retina of your eye to collect more light than normally possible. It does so by utilizing an objective lens (the one used by a refractor telescope) or a primary mirror (the one used in a reflector telescope) to collect light and bring it to a point (or focus), and an eyepiece lens, which spreads the light out over the retina of your eye and magnifies it, so that the tiny writing on your stamp we discussed earlier is now legible to you
In the simplest terms, when we use a basic telescope, a big lens (or mirror) takes in the light, focuses it, and then a second one brings the light (with the image) to our eyes through an eyepiece, enlarging and revealing details of the object we are looking at.

A telescope utilizes some other features in addition to the ones we already mentioned, which determine how well it can collect, how much it can magnify the image and how the resulting image will appear:

1) The aperture of the telescope – the diameter of the lens or mirror that is utilized to gather light. The larger the aperture is, the more light the telescope is able to collect and bring to a point (or focus) and the greater the brightness of the resulting image. It also plays a role in the objects’ resolution.
2) The telescope’s magnification, performed by the eyepiece – its ability to expand an image. It largely is determined by the combination of lenses used. (Lenses are usually either concave (lens or mirror that causes light to spread out) or convex (lens or mirror that causes light to come together to a focal point).

Here are some interesting telescope terms you want to be aware of, especially when purchasing your first scope:

* Aperture of the telescope this is the diameter of the lens or mirror that is utilized to gather light and the most important consideration when buying a telescope! The greater the aperture, the better!

* Magnification (power) this is the telescopes ability to enlarge an object; it is calculated by dividing the telescope’s focal length by the eyepiece’s focal length. telescope with a given eyepiece.

* Focal length this is the distance required by a lens or mirror to bring the light to a focus.

* Focal ratio or f/number – The focal ratio is calculated by dividing the focal length of the objective lens or primary mirror by the aperture. It plays a role in determining the brightness of the image and the width of the field of view.

* Resolution – measures how close two objects can be to each other and yet still be detected as separate objects (important for revealing fine details of an object and usually measured in “arc-seconds”)

* Wave number or wave error The smaller the wave number, the better the mirror or lens. As a rule, you should accept no less than a wave number of one-fourth, but good telescopes generally have wave numbers of one-eighth or less.

Lastly, regardless of what kind of telescope you use, it is best to observe the night sky in an area far away from city lights. That way the city lights will not overpower the “lights” of the sky! To enhance your telescope experience further, make sure to check websites like, and for upcoming “space events”.

So, now you know the basics of a telescope! Happy observing!