Telescopes

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Slide 1

Telescopes

How do they work?

Slide 2

1. History

2. Lenses & Hardware

3. Reflecting Telescopes

4. Refracting Telescopes

Slide 3

History

Hans Lippershey Middleburg, Holland

invented the refractor telescope in 1608

Galileo

the first to use a telescope in astronomy. Galileo's designs used a combination of convex and concave lenses.

Kepler

improved the design to have two convex lenses, which made the image upside-down. Kepler's design is still the major design of refractors today, with a few later improvements in the lenses and the glass to make them.

Slide 4

Why can’t you see an object that is far away?

The answer is simple: the object does not take up much space on your eye’s screen (retina).

Using a digital camera analogy, at 150 feet the writing on a dime does not cover enough pixels on your retinal sensor for you to read the writing.

This can be corrected by bending the light with lenses.

Slide 5

Lenses

The lens in your eyes works like a glass lens. The light bends as it goes through a different medium.

Light rays are bent when they intersect glass; a curved surface can produce an image.

In your eye, the image is then focused at the retina.

Slide 6

How does this apply to telescopes?

If you had a bigger eye, you could collect more light from the object. This image could be magnified so it stretches out over more pixels in your retina.

In a telescope, two pieces make this possible:

the objective lens (refractor telescopes) or primary mirror (reflecting telescopes)

the eye piece

Slide 7

The objective lens (in refractors) or primary mirror (in reflectors) collects lots of light from a distant object and brings that light, or image, to a point or focus.

An eyepiece lens takes the bright light from the focus of the objective lens or primary mirror and "spreads it out" (magnifies it) to take up a large portion of the retina. This is the same principle that a magnifying glass (lens) uses; it takes a small image on the paper and spreads it out over the retina of your eye so that it looks big.

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