1. Telescopes

2. Images can be formed through reflection (mirror) or refraction (lens). Reflecting mirror Optical Telescopes

3. Refracting lens Optical Telescopes

4. Reflecting and refracting telescopes Optical Telescopes

5. Modern telescopes are all reflectors (use a mirror): Light traveling through lens is refracted differently depending on wavelength. Some light traveling through lens is absorbed. Optical Telescopes

6. Image acquisition: Charge- coupled devices (CCDs) are electronic devices, can be quickly read out and reset. Optical Telescopes

7. Interferometry: Combines information from several widely spread radio telescopes as if it came from a single dish. Radio Astronomy

8. Infrared radiation can image where visible radiation is blocked; generally can use optical telescope mirrors and lenses. Other Astronomies

9. Much can be learned from observing the same astronomical object at many wavelengths. Here, the Milky Way. Other Astronomies

10. Electromagnetic Spectrum  All the types of radiation are shown on the electromagnetic spectrum from long wavelengths (radio) to short wavelengths (gamma).  We can only use our eyes to see a very small portion of the radiation that is emitted in the universe (visible light)

11. Electromagnetic Spectrum