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Doing Science

Unit Four: Investigating Tools of Astronomy
Doing Science

2. Selecting a Telescope Site

Telescopes are our "eyes into the universe." Commonly, questions about specific telescopes revolve around what kind of a telescope it is, how big it is, or what the highest magnification is. Less common are questions about where the telescope is, and why it was built where it is. In reality, finding a suitable site is an important part of any project to build a new telescope, large or small. But where have telescopes been built, and why? One way to approach these questions is to look at where on Earth existing telescopes are located and compare the conditions at each site.

Obtain a map of the world that you can make marks on. This can be either a paper copy or an electronic copy if you have software available that can mark the map. The map also needs to show latitude and longitude. A good source for electronic maps is the University of Texas' Perry Castenada Library Map Collection:

Next, locate a list of the world's largest modern telescopes, and a list of the largest telescopes built in the 1700 and 1800s. The list needs to include where the telescopes are located, by place name or by latitude or longitude. A good list of modern telescopes can be found at:, and a good list of older telescopes can be found at: Look at both the "Largest Telescope" list at the top of the web page, and the "Almost the world's largest telescopes" list somewhat further down the page to get information about telescopes built between about 1760 and 1908. You may need to do an Internet search to find the locations of some of the observatories.

Now mark the locations of all the observatories built before 1900 using one color or symbol, and mark the locations of all the post-1900 telescopes using another color or symbol. Do you see any patterns in the locations of the newer and older telescopes? Any changes between the two eras of telescope building? Compile a list of the characteristics of the important pre- and post-1900 observatories and look for patterns. Consider factors such as elevation, annual cloud cover, strength and directions of prevailing winds, local population density, and geographic setting (mountains, valleys, plains, rivers, oceans, lakes, etc.).

Your Report:
Prepare your map for presentation in either a paper or PowerPoint format. Provide a written discussion of the factors you have found that are important in locating telescopes past and present, or make a presentation of your conclusions to your class.