Optical Powers

Teacher Page
Activity 1 Introduction to Telescopes

Standards (see Appendix A):

Unifying Concepts:  Form and Function; Systems; Order and Organization.


The students will begin to understand how telescopes are tools of the astronomer.  Telescopes function as systems, with mirrors and/or lenses that gather and focus light from distant sources in the sky to create images which can be seen through an eyepiece.  Astronomers attach cameras or detectors to telescopes in order to record images and collect data for analysis. 


This activity provides students with experience looking at different kinds of telescopes sufficient to begin exploring the questions:

  1. What are the different parts of a telescope?
  2. Why are there different kinds of telescopes?
  3. What is needed to sense or record data from a telescope?
  4. How do telescopes assist astronomers in making observations of far away objects that appear very faint or small?

Historical Background: 

Galileo was the first scientist to use telescopes for the study of astronomy.   The story is told that Galileo was made aware of a new device apparently from Amsterdam invented by an optician, which allowed objects at a distance to be viewed more easily.  Galileo took the idea of the telescope and began to make technological improvements on it.  He soon had a device that he could market to politicians and to the merchants of Venice.  They were able to see faraway ships at sea approaching the land.  Some of these ships could have been enemies; telescopes provided advance warning of attack.  Other ships were carrying goods for trade.  With the help of the telescope, merchants could manipulate the price of commodities and make larger profits off each shipload of goods.  The merchants were grateful enough to Galileo that they set him up with a good income and a university chair.  Galileo used his telescope to make many new discoveries about the solar system.  He discovered craters on the moon, phases of Venus, the moons of Jupiter, and sunspots.  He used his discoveries to support Copernicus's heliocentric model of the universe.

Use the web to research Historical Telescopes:  This site contains a brief history of the building of telescopes and the people who did the construction. http://es.rice.edu:80/ES/humsoc/Galileo/Things/telescope.html. 

Go straight to the source, the Museum of Science in Florence Italy, for information about Galileo.  http://galileo.imss.firenze.it/museo/b/egalilg.html

Recommended Literature:  Galileo’s Daughter by Dava Sobel, Walker & Company, 1999.  http://www.galileosdaughter.com/home.shtml

Technical Background:

SAFETY:  Never point a telescope at the Sun.  Do not look through magnifiers, binoculars or a telescope pointed at the Sun.  (The only safe way to view the sun is through specialized solar filters placed over the large end of the telescope, filtering the light before it passes through the telescope optical systems.)

Students will experiment with telescopes and imaging systems throughout this curriculum, where concepts and technical vocabulary concepts will be developed.   This lesson is meant only as exploratory. The following summary is provided as background for the teacher.

Telescopes are systems containing

The purpose of a telescope system is to

Important terms


Gather a picture or pictures of the sky.

So your students become familiar with telescopes, gather pictures of telescopes or arrange for an amateur astronomer to bring a telescope to class.  Best yet, arrange for a Star Party with the help of your local amateur astronomy club or planetarium. 

Time:  approximately 30 - 40 min.


Prior to this activity, have each student bring in a picture of a telescope.  Students should record any information that is readily available about their scope.  The student page for this activity has links to telescope pictures.  You may wish to have students view these pages instead of or in addition to collecting pictures of telescopes. 


  1. Begin by displaying any picture of the night sky.  Tell the students that in this picture there is a small cluster of stars that they have been asked to investigate.  You may point to any starry or fuzzy area on the picture or even a blank spot, claiming that as the location of the cluster in question. 
  2. Ask: Why is investigating this star cluster going to be difficult? Challenge the students to think about this problem.  The cluster of stars may appear small and dim to us.  Do we know it is small?  It might be very big. Is it really dim, or just far away? 
  3. Ask:  What is the primary tool that astronomers have available to them to overcome the problems of distance and dimness?  Most students will know that astronomers use telescopes.    If students gathered pictures of telescopes for home, they can Student homework was to gather pictures of telescopes.  Since it is difficult to see parts of scopes from pictures if you have no actual experience with real telescopes, the best option is to have actual telescopes available to view.
  4. Ask students to share the telescope pictures they gathered for homework or share the notes they made about telescopes they viewed on the web pages linked to the Student Page.  Ask: Do all these telescopes look the same? What do all these telescopes seem to have in common?  List parts: mirrors, lenses, tubes, mount, tripod or base of some sort etc. Record all responses on the board, an overhead or on butcher paper.
  5. Ask:  Telescopes can look very different but what are the things that astronomers want all telescopes to do?  Students may  recognize that telescopes need to make things look brighter, bigger, and show detail clearly.  However, they may not understand how the the parts of telescope systems work together to accomplish these goals.  Record all responses.  Try for some degree of agreement among the group as to what will be put on the list. 
  6. Anther question:  Why do you think there are so many different telescopes? Students might consider the different observing projects or different science objectives or different budgets or available technologies that would lead to the building of different kinds of telescopes.
  7. Explain to the students that they will be doing a series of investigations that will allow them to explore the different properties of  telescopes.   They will be learn how the properties of a telescope and the CCD imaging system affects images produced by that telescope.  The activities should provide for students a basic understanding about what kind of telescope would be most useful for imaging a particular target or for conducting an observing research project. 


This activity is designed to stimulate interest in the technology of telescopes and to help you assess the level of prior knowledge of the class as a whole.