How Telescopes Work

Kristi Walker's image for:
"How Telescopes Work"
Image by: 

How Telescopes Work

I remember the first time that I looked through my Dad's telescope lens. He loved all things scientific, especially if they could be observed while he was outdoors! I saw the surface of the moon for the first time through the lens of my Dad's scope. It looked like it was so close that I could touch it. I was hooked. That telescope succeeded in beginning a lifelong love affair with physics.

In 1608, a Dutch eyeglass maker placed 2 lenses, one in front of the other, and discovered that he could see things, magnified. The concept of the telescope was born. Telescopes work by focusing light from distant objects to form an image. An eyepiece then magnifies this image for your eye.

There are 3 types of telescopes. There are refractors, reflectors, and telescopes that incorporate both concepts.

1. Refracting telescopes are the most widely used and oldest form of telescope. They work by "bending" light through convex and flat glass. The lens at the end of the telescope is curved and will collect the light from the far away object. It's curved head will focus the light and magnify it. The flat lens will then "straighten" the light and allow the human eye to see it. The eyepiece will also magnify the object and, along with the flat lens, allow the human eye to see it as normal.

2. Reflecting telescopes use mirrors instead of lenses to manipulate the photons(light) of the far away object. The first reflecting telescope can be credited to Sir Isaac Newton. It is still the most popular reflecting scope and is still very popular with true astronomers today. Because light is distorted when using lenses, the mirrors will show a "truer" image. However, they do "flip" the image you are viewing. This is not relevant unless you are searching for north or south poles. Reflecting scopes give much truer color than refracting scopes and for this reason, many amateur astrophysics buffs use them. Keep in mind that they are much harder to keep clean. The mirrors can become foggy and dirty when using the scope outside.

3. For the third kind of telescope, think Hubble or Keck. These incorporate both reflector and refractors and would not be feasible for the amateur or common astronomer.

I think that to cover the workings of the telescope we must cover not only "how" they work, but what you need to look for if you decide to purchase a telescope of your own. Purchasing, for your specific needs, is relevant in "how" your telescope will work for you.

1. Steer clear of department store telescopes. They are that cheap for a reason. They typically use plastic optics (lens') and if you think that light bends drastically when going through glass, try to get it to go through plastic! They're not worth your hard earned money.

2. Large print announcing "great magnification" should be steered clear of, too. Magnification is over-hyped. The magnification of your telescope is controlled by your eyepiece. Not the telescope itself. What you are looking for is a low powered eye-piece with a wide field of range. This will allow more light to enter your eye, and therefore provide a clearer picture. Large telescope magnification will only increase optical flaws and increase the rotation of the earth. So beware!

3. Choose a telescope mount wisely, as well. Your primary concerns for your mount will be portability, stability and point of tracking.

4. The eyepiece on your telescope is very important. This is your window through your telescope. The eyepiece is the small, removable lens that you actually look through. Remember if you purchase more eyepieces for your telescope, to match any eyepiece to the aperture for the clearest image!

As a side note: skip the computer soft-ware. They are typically worthless and almost no help at all. Buy a good astrophysics book and you will find them much more helpful. And they can be brought along with you!

Finally, like Galileo and Newton, you can be fascinated by the world around you. You do not need to be a physicist to appreciate all that you see. You just need to be able to "see" it. There is more out there than the moon. A good telescope will give you a new set of eyes. Eyes that see the phases of Venus, some of Jupiter's moons, comets, nebulae or perhaps even gazes of the Great Spiral Galaxy. The beauty of space and all she holds is at the end of that telescope lens.

More about this author: Kristi Walker

From Around the Web