1. How Stars are Seen…
Astronomy - Ch.20

2. Naked Eye can see ≈ 5000 stars

3. The Optical Telescope gathers light by focusing it through a lens or mirror – now we can see many more stars!

4. The Optical Telescope
COLLECTS LIGHT: over minutes or hours to create digital or chemical photography
Enables DISTINCTION between distant objects
MAGNIFIES the images formed

5. The Refracting Telescope
Using a large glass lens (objective) the light is refracted (bent) to a small lens (eyepiece)
Light travels through the glass lens
Ex: Binoculars, Small Telecsopes

6. The Reflecting Telescope
Uses a curved mirror to gather and focus the light
Largest optical telescopes are reflecting telescopes
Ex: Hubble Space Telescope

7. The MMT (Multiple Mirror Telescope)
Several small, low-cost mirrors replace on expensive large mirror
Less expensive to build than telescopes requiring one large mirror
The MMT (Multiple Mirror Telescope)

8. The Schmidt Telescope
Combination of refracting-reflecting telescope with a wide field of view
Found at almost all observing sites

9. The Hubble Space Telescope
Designed to orbit high above the interference of Earth’s atmosphere, therefore very clear images
Size of railroad boxcar
610 km above Earth’s surface

10. Beyond Visible Light
We can use optical telescopes to study the visible light from stars, but not all forms of energy are visible
Stars emit x-rays, radio waves, infrared waves and other kinds of electromagnetic energy

11. The Electromagnetic Spectrum
ELECTROMAGNETIC ENERGY
Forms of Energy that travel at the speed of light ( km/s), each with its own frequency and wavelength
ELECTROMAGNETIC SPECTRUM
Total range of electromagnetic waves, from radio waves to gamma rays