How Telescopes Work

A telescope is a device that allows us to bring distant objects closer to us so that we can study them. A good example is the many planets, galaxies, and stars in outer space. Some range from $1 at the toy store to the $1.2 billion Hubble Telescope. There are two types of telescopes. Refractors use a glass lens. Reflectors use mirrors instead of a lens.

Let's take the different pieces of a microscope and see how they work. The objective lens in a Refractor or primary mirror in Reflectors gather incoming light and brings it to a focus. The eyepiece takes that same light and magnifies it to take up a large part of the retina of the eye. Thus, it takes a small image and spreads it out to make it look bigger.

There are two general principles to any telescope. One is how well it can collect light. The other is the magnification of the image you are viewing. Collecting light is related directly to the diameter of the lens. The more light collected, the brighter the image.

Magnification is the ability to take an object as a far distance and enlarge it so you can see it clearly. Any magnification can be obtained by using different eyepieces depending on the object you are trying to view.

Here is a simplified explanation. Obtain two magnifying glasses and a piece of paper. Hold one of the glasses between you and the paper. At this point, the image will be blurry and unreadable. Take the second glass and place between your eyes and the first glass. Moving the second glass up or down should bring the piece of paper into view. It will be larger and upside down though. Give it a try and see what happens.