1. How Telescopes Work
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Students will learn three simple telescope designs while comparing and contrasting telescopes. Students will then relate telescope designs to the Highland Road Park Observatory developing a basic understanding of how the Park’s telescope works.


Students need to have a basic understanding of how Observatories’ telescopes work in order to utilize the information that they will be gathering when completing various lessons on space images. After completing the simple demonstrations the students will have a better understanding of basic telescope design.


Students will:
  1. Sketch and label three basic types of telescopes.
  2. Demonstrate an understanding of telescope design by completing activities with magnifying glasses and mirrors.
  3. Apply knowledge of telescope design to the Highland Road Park Observatory telescope.


SI-M-B3, SI-M-B7, SI-H-A3, SI-H-B3


Overheads or sketches of the 3 basic types of telescopes, 2 different sizes of magnifying glasses, mirror, magnifying mirror (the kind someone would use to shave or put make up on with), pictures of different types of telescopes.


  1. From huge reflectors 1,000 feet wide to tiny binoculars you can fit in your pocket, most telescopes work in basically the same way – they collect and focus light to bring distant objects close up. A general property of a telescope is how will it collect light.
  2. Have students complete the following telescope demonstrations.

    Demonstrating a Refracting telescope:


    2 magnifying glasses (it works best of one magnifying diameter is larger than the other), a sheet of paper with words on it.
    1. Hold one magnifying glass (the bigger one) between you and the paper. The image of the print will look blurry.
    2. Place the second magnifying glass between your eye and the first magnifying glass.
    3. Move the second glass forward or backward until the print comes into sharp focus. You will notice that the print appears larger and upside down.
      **This is similar to how a refracting telescope works. Light enters the objective lens and then passes through the eyepiece lens before it can be focused. The image you see is larger and upside down. 

    Demonstrating a Reflecting telescope:


    flat mirror, magnifying mirror (the kind adults use to shave with), magnifying glass, and flashlight.
    1. Place the magnifying mirror on a table to reflect the simulated sun (flashlight). Adjust the mirror so that it stands at an angle to the window so that the reflected light is visible against the window or the wall next to it.
    2. Prop up the flat mirror between the magnifying mirror and the window or wall, in the path of the reflected light. From behind the magnifying mirror, you should see its reflection in the flat mirror (you could also do this demonstration at night. You will need to adjust the position and angle of both mirrors to get a good reflection of the moon or a group of stars. After every few minutes you will have to readjust the mirrors because of the motion to the moon and stars).
    3. Use your magnifying glass to examine the reflection that appears in the flat mirror. Move the magnifying glass back and forth until you see the reflection clearly. How well your telescope works depends on the quality of your magnifying glass and on finding the right distance and angles between the mirrors. Groups will have to problem solve to find the best view.
    4. To simulate the sunspots you can attach black spots on the flashlight or shine the flashlight onto a round object to simulate the moon for the students to reflect into the mirror. ***BE SURE TO TELL THE STUDENTS NOT TO VIEW THE REAL SUN, THIS MAY DAMAGE THE EYES.


    1. Using overheads or copies (print the attached sketches and make overheads or copies) of the three basic types of telescopes, lead a class discussion on the telescopes relating the demonstrations to the various telescopes. Have students sketch each telescope diagram and copy the basic definition of each.
    2. Teachers can begin with Cool Facts from How stuffworks.com “How Telescopes Work” 
      Cool Facts taken from http://www.howstuffworks.com/telescope1.htm
      • The smallest telescopes available today are more powerful than the one Galileo used to discover the wonders of the solar system!
      • With an amateur telescope, you can see anywhere from 40 million to a half-billion light years into space!
      • Your telescope is a time machine!
        When you look far into space, you are looking back into time! Light from distant objects takes time to reach us (one light year is the distance traveled by light in one year). For example, the light from an object that is 40 million light years away left that object 40 million years ago. Therefore, you see the image of that object, as it appeared 40 million years back!
      • Today, you can get a commercially available telescope that is almost as big as those used by professionals!
      • You can do serious science with your telescope!
        Many amateur astronomers contribute to the science of astronomy. Amateurs have much more time to spend on the "little things" than professionals do. Furthermore, the price of large aperture telescopes has come down so much over the years that many amateurs now have equipment that rivals the stuff used by professional astronomers. Amateurs can contribute in many areas, such as variable star observing, meteor counting and comet hunting.
      • A Baton Rouge high school student discovered an asteroid.
    3. For more information that can be used in the class discussion go to http://www.howstuffworks.com/telescope1.htm This site takes you not only through different types of telescopes but tips on how to purchase the best telescope for you. Refracting and Reflecting telescope images taken from this site.
    4. There are three basic types of telescopes:

      1. Refractor – a lens is the primary device for gathering light

      2. Reflector – a mirror is the primary device for gathering light.

      3. Compound – a combination of lenses and mirrors is used to gather light
    5. The teacher can decide to what extent to discuss key items. All item are covered more thoroughly on the site http://www.howstuffworks.com/telescope1.htm

    Basic Telescope Terms:
    1. Field of view – area of the sky that can be seen through the telescope with a given eyepiece.
    2. Focal length distance required by a lens or mirror to bring the light to a focus.
    3. Focal point or focus – point at which light from lens or mirror come together. 
    4. Aperture – a telescopes ability to collect light, this is related to the diameter of the lens or mirror that is used to gather light. The larger the aperture, the more light the telescope collects and the brighter the final image.
    5. Finder scope – a device used to help aim the telescope at its target, similar to the sight on a rifle.
    6. Telescope Mount – a type of stand that supports the telescope.
      There are two basic types 
      A) Alt-Azimuth mount has 2 axis of rotation, a horizontal axis and a vertical axis. 
      B) Equatorial mount has two perpendicular axis of rotation, right ascension and declination; it is tilted at the same axis as the Earth’s axis of rotation. To see an animation of the basic mount movements go to- http://www.howstuffworks.com/telescope5.htm
    7. Magnification (power) – telescope’s focal length divided by the eyepiece’s focal length.
    8. Resolution – how close two objects can be and yet still be detected as separate objects, usually measured in arc seconds (this is related to the telescopes aperture).

    Telescope History:

    1. Hans Lippershey is credited for inventing the refractor telescope in 1608.
    2. Galileo was the first to use the refractor telescope in astronomy.
    3. Kepler improved the refractor’s design in 1611.d. Isaac Newton developed the reflector about 1680.
    4. Bernhard Schmidt a German astronomer made the first compound telescope.
    5. The Hubble Space Telescope is a Schmidt-Cassegrain design.
    The Schmidt-Cassegrain design, which was invented in the 1960s, is the most popular type of telescope; it uses a secondary mirror that bounces light through a hole in the primary mirror to an eyepiece.

    Relating Highland Road Park Observatory to telescope information:

    1. Print out Teacher Information On Highland Road Park Telescope.
    2. Over the next few lessons we will be using images from the Park’s telescope, therefore it would be beneficial for the students to have an understanding of what makes up the telescope. 
    3. Using the knowledge gained from this lesson, relate to the students the basic make up of the telescope. Have students record the size of the scope, the kind of the mount, size of the primary and secondary mirrors, and camera type.


      After completing the demonstrations assign the students to select on of the demonstrations, sketch and explain what took place and relate the demonstration to how they think this demonstrates how a telescope works. Teachers collect and use the rubric to assign grade. 

      Demonstration Rubric: 

      Sketch - 0 to 25 points 
      Mirror and magnifying glasses labeled – 0 to 25 points
      Explanation of sketch – 0 to 25 points
      Explanation is in complete sentences – 0 to 25 points

    Internet Resources: 

    http://es.rice.edu/ES/humsoc/Galileo/Things/telescope.html Telescope History. Discusses early inventers and includes sketches of first telescopes. 

    http://www.howstuffworks.com/telescope1.htm This site takes you not only through different types of telescopes but tips on how to purchase the best telescope for you. 

    http://school.discovery.com/lessonplans/programs/hubble/index.html Students will understand the following:

    1. The Hubble Space Telescope lets us see farther into space than ever before.
    2. The Hubble gives us images that are thousands of years old because light travels at a finite speed across vast distances of space.
    3. The Hubble could be used to search the universe for other Earthlike planets, but such exploration is expensive.
    4. There are arguments for and against spending money to look for other Earthlike planets that might be thousands of light-years away. 

    http://spaceplace.jpl.nasa.gov/wfpc_fact1.htm How good is the Amazing Hubble Space Telescope? Includes some basic activities along with facts on the Hubble Telescope. 

    http://spaceplace.jpl.nasa.gov/ki_do1.htm Keck Interferometer Crossword Puzzle and information on Keck Telescopes, the world’s largest telescopes, located in Mauna Kea, Hawaii.