Types of Telescopes - Josh Gaskin
[1] - Double click to view references


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The best type of telescope for space exploration is the reflector telescope. It is very effective because the mirrors are in a parabolic shape that reflects the parallel rays of light travelling towards the earth from outer space. Although these types of telescopes are therefore very large, making them available in observatories


What is a Telescope?


A Telescope is an optical instrument used for making distant objects appear large and therefore closer than they actually are. The first known telescope was used and made famous by Galileo Galilei, a famous astronomer and mathematician who wanted activity on the sun in the late 1500's and early 1600's. The two main types of telescopes to used it to observe the moons of Jupiter, the phases of Venus, and the sunspot are the reflector telescopes and the refractor telescopes. In addition there are terrestrial telescopes and astronomical telescopes. All types of telescopes have different features to them, such as lenses, size (length and width), how light effects the telescope (how much light, or where it is distributed), or how the mirrors are aligned.












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This is what a standard Telescope looks like, although there are many different types, each of which are better than others for accomplishing certain tasks. This is why it is a good idea to find out what types of telescopes work best in each different situation, so that you know what the best type of telescope is when necessary

How have telescopes benefited human development, and our understanding of technology?


Telescopes, even when they were first invented back in the middle ages, have been allowing astronomers to view the solar system that we are a part of, as well as the rest of our galaxy, and even the entire universe. The discoveries that have been made by using telescopes had had large benefits to humans. We now know how our solar system works, and how the Earth relates to all of the other planets and stars. We know that the universe is always expanding, and that all of the planets in our solar system orbit the sun. Telescopes helped us learn more about the Earth's rotation, revolution, and the moon. Finally, because we have learned so much more thanks to telescopes, we can now learn about outer space in school.



Reflector Telescopes


Reflector Telescopes uses mirrors to concentrate and collect the light. These telescopes can spot objects far out in space, this is because the light rays travel in straight, parallel rays, which travel into the telescope. The parabolic shape of the mirror reflects the rays and focuses them to a small spot which can then be viewed by researchers, scientists, or astronomers. A common defect in refractor telescopes is chromatic abberation. However an advantage that the reflector telescopes have is that they do not suffer from this problem, because the parallel rays of light all reflect off the telescope in the same direction. Also although they are usually the preferred telescope by astronomers, the average refractor telescope would usually cost more than a reflector telescope, even if both of them were the same size. The final advantage of reflector telescopes is that because they reflect light on only one side, only one side of the objective needs to be in good condition.Unfortunately there are disadvantages to the reflector telescope too. Since the telescope is used for long range purposes the optics can easily come out of alignment. Also the top part of the telescope, including the optic, is outside, which means that it requires frequent cleaning in order for it to work at the highest efficiency possible. Finally a secondary mirror is commonly used in reflector telescopes, and it can become deficient and create a blurry effect on bright objects over time.
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This is a Diagram of a Ray of light passing through a reflector telescope


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This is a large reflector telescope located in an observatory



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Spherical Aberration is a defect that can occur to both reflector and refractor telescopes, it is when all of the light does not focus on the same point.The main cause of this is when the mirror is not curved as much as it should be.





Refractor Telescopes


Usually noted as being inferior to the reflector telescopes, refractor telescopes use glass lenses instead of mirrors as their objective. So instead of reflecting light like a mirror, the lenses cause the light to bend. This bending of rays of light is called refraction and this is also how this type of telescope got its name. The first advantage of refractor telescopes, is that the optics are very good at staying aligned, so that when you are looking through the telescope, everything appears where it should, and there are now odd effects created. Also, unlike the reflector telescopes, the top of the telescope is sealed by a glass surface, so it does not need to be cleaned very often. Finally, because the top is sealed from the outside, different weather effects or air pressure will not affect the image created and allow for objects to be seen with much more clarity and steadiness. Just like in the reflector telescopes, there are some factors that make the telescope worse, and lower its productivity. The first disadvantage is called Chromatic Abberation. This is created by the light bending through the lens, and creating a visible spectrum, although this may look interesting, the rainbow colours around your image can ruin the clarity, and you may not be able to see certain features of the image. Also, because a lens is used, and not a mirror, both sides of the lens need to have a perfect curvature, unlike the mirrors in the reflector telescopes, where only one side needs to be in good condition. The final disadvantage of refractor telescopes is that because of the weight of the lens, the objective can only be supported at the ends, making it more difficult to place in the telescope.


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This is a diagram of a ray of light passing through a refractor telescope



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Refractor telescopes can be found as the sights on sniper rifles such as the M40A3 seen in this picture


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Another example of the refractor telescope in this ACOG scope


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A typical terrestrial telescope


Terrestrial Telescopes


Terrestrial telescopes are refractor telescopes that have inverted lenses or an eyepiece to show an upright image. This type of telescope isgenerally used for making observations on Earth only, as it is not built for the long ranges that the astronomical telescope is. These types oftelescopes are also made so that they are portable, and are usuallyfairly easy to transport from one place to another.

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A typical astronomical telescope

Astronomical Telescopes


Astronomical telescopes are designed for mounted use in an observatory. They are reflector telescopes that usually result in an inverted image.These telescopes are used for viewing objects in outer space, and are used by astronomers. Astronomical telescopes are meant for long ranges,unlike terrestrial telescopes which are generally built for closer ranges (in comparison to the very long ranges of the astronomical telescope) thatare all within the Earth.




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Practice Quiz /5


1) What telescope is the best for viewing objects in outer space?
2) Who was the first astronomer to use the telescope and make them famous?
3) What type of telescope uses mirrors? Which uses Lenses?
4) What telescope is portable and is used for viewing objects at shorter range (within the Earth)?
5) In your opinion what type of telescope would you prefer? why? Give evidence from the wiki article to support your reasoning.


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Recent News Article


NASA' Kepler mission was designed to track super flare (giant solar flares) activity in outer space.
This activity has been recorded and monitored throughout the past few years.In a recent article (may 16th)
The records have been finalized and publicized. There are many stars that are very similar to our sun that
can produce these massive bursts of energy and light. This has all been monitored using telescopes, most
likely Astronomical telescopes with reflector objectives.









  1. ^ References
    -www.typesoftelescopes.org
    -www.astronomynotes.com/telescop/s2.htm
    -www.astronomynotes.com/telescop/s3.htm
    -www.coolscopes.com/terrestrialscope.html
    -www.dictionary.com
    -http://inventors.about.com/od/gstartinventors/a/Galileo_Galilei.htm
    -www.skyandtelescope.com/news/Superflares-from-Sun-like-Stars-151753935.html
    -http://topics.nytimes.com/top/news/science/topics/hubble_space_telescope/index.html