How Does a Refracting Telescope Work?
A refracting telescope works just like a magnifying glass. It uses a convex
glass lens (to bend light and bring it into focus. This lens is thicker in the
center than it is toward its edges, which bends the light more at the edge of
the lens than light coming through the center. This allows all of the light to
come together at a focus point. The point of focus is where the image is
created.
If someone looks into the eyepiece, a concave lens magnifies the image.
Refracting telescopes have two main problems—images are not always clear
because the light is being bent and the size of the lens is limited (which
limits the power of the telescope).
History of the Refracting Telescope
A Dutch optician (someone who makes lenses for glasses), Hans
Lippershey,
designed the convex lens for the first refracting telescope in 1608. He found
that a distant object appeared to be much closer when he looked at it through a
concave lens and a convex lens held in front of each other. He put the lenses
into a tube to make the first refracting telescope.
Galileo Galilee made the first refracting telescope used to study space in
1609. He used it to discover four of the moons orbiting Jupiter. Galileo also
used his refracting telescope to map the surface of the moon. Galileo could see
objects 20 times smaller than the human eye could using his telescope.
How Does a Reflecting Telescope Work?
Reflecting telescopes use curved mirrors instead of convex lenses to collect
and focus light. A large concave mirror (the center is thinner than the edges)
collects and reflects the light to make an image. Once the image forms, the lens
in the eyepiece magnifies the image. Reflecting telescopes are very helpful for
viewing dim or dark objects. Large reflecting telescopes can see objects that
are a millionth or a billionth the brightness of the faintest star that can be
seen by the human eye alone!
History of the Reflecting Telescope
A Scottish astronomer, James Gregory, came up with the design for the
reflecting telescope in 1663. Isaac Newton made the first model of the
reflecting telescope in 1688. After Newton built the model, scientists
discovered that better images are seen through the reflecting telescope instead
of the refracting telescope because mirrors could make clearer images since the
mirrors could be made much larger than the lenses. The reflecting telescope is
still used today.
