and other devices for looking at the universe.

Reading: Chapter 6, Optics and Telescopes

What kind of electromagnetic radiation from space can we detect on Earth? Before this century, astronomer could only observe in the optical region. Then radio was added. Finally, with space satellites, we have observations across the whole electromagnetic spectrum.

Radio & microwave

Use earth based detectors ("radio telescopes.") In order to be able to point the telescope in a certain direction of interest, it needs to be large. (For good pointing, need a size much bigger than the wavelength of the radiation.) So people use a big dish shaped object.

You are familiar with this because the same shaped objects are used to pick up TV signals from satellites.

To get better angular resolution, you can connect several dishes with electronic links. With suitable electronics, this gets the angular resolution of one giant dish.


Use a telescope based on a mirror.

Use a diffraction grating to divide the light from a star (or other object) into its colors.

Space based observations.

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA