Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Support PBS Shop PBS Search PBS
Genoa, Italy (1625 - 1712)
Giovanni Domenico Cassini was an Italian mathematician, astronomer, engineer, and astrologer. Cassini was an astronomer at the Panzano Observatory, from 1648 to 1669, professor of astronomy at the University of Bologna and became, in 1671, director of the Paris Observatory. Along with Robert Hooke, Cassini is given credit for the discovery of the Great Red Spot on Jupiter (ca. 1665). Cassini was the first to observe four of Saturn's moons, which he called Sidera Lodoicea. Around 1690, Cassini was the first to observe differential rotation within Jupiter's atmosphere.





The Glass & Mirrors Toolkit

If you have access to some lenses and mirrors in your school science supply room, this set of demonstration activities will help your students understand more about how telescopes work, the differences between telescopes made with mirrors and those made with lenses, and how we are continuing the tradition of Galileo and Newton in building new telescopes today.

Big Questions

How do telescopes actually work?
Why are bigger telescopes better?
What’s the difference between telescopes made with lenses (refractors) and telescopes made with a mirror (reflectors)?
How are the telescopes of Galileo and Newton similar to telescope designs today?

Big Activity

Using a simple setup with lenses and mirrors, demonstrate how a telescope collects light, focuses it, and then magnifies the image.


Presenters: A minimum of one person.
Visitors: Up to 10 people at a time is appropriate.


About 15 minutes.

The Glass and Mirrors manual is a 34-page PDF file. Click here to download.

Contributed by Astronomical Society of the Pacific.




The Film | Video | For Teachers | Schedule | News | Planetarium Program
Newsletter | IYA Calendar | Resources | Glossary | Contact Us | Site Map

© 2009 Interstellar Studios. All rights reserved.