How do they work?
2. Lenses & Hardware
3. Reflecting Telescopes
4. Refracting Telescopes
Hans Lippershey Middleburg, Holland
invented the refractor telescope in 1608
the first to use a telescope in astronomy. Galileo's designs used a combination of convex and concave lenses.
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.
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.
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.
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
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.