1. Telescopes

2. Act as “electromagnetic radiation catchers” Capture as much as possible Focus Magnifies images Telescopes that “catch” visible light are called optical telescopes. (4)

3. Telescope Terms magnification (power) – how strong the telescope is. resolution - how close two objects can be and yet still be detected as separate objects. aperture – diameter of the lens or mirror

4. Refractor Telescopes (5) Hans Lippershey of Middleburg, Holland, gets credit for inventing the refractor in 1608, and the military used the instrument first. Galileo (1609) is the first to use it for astronomy. The objective lens gathers the light, and bends or refracts it to a focus near the back of the tube. The eyepiece lens brings the image to your eye, and magnifies the image. (5) Refractors have good resolution, high enough to see details in planets and stars. It is difficult to make large objective lenses (greater than 4 inches or 10 centimeters) for refractors. Refractors are relatively expensive

5. Refractor Telescope Diagram

6. Reflector Telescopes(5) Isaac Newton developed the reflector about 1680. Newton used a curved, metal mirror to collect the light and reflect it to a focus. (5) Because the mirror reflected light back into the tube, he had to use a small, flat mirror in the focal path of the first mirror to deflect the image out through the side of the tube, to the eyepiece; otherwise, his head would get in the way of incoming light.

7. Reflector Telescope Diagram

8. Refractor vs. Reflector

9. Radio Telescopes (4) Karl Jansky inadvertently discovered galactic emissions of radio waves in 1933 Like optical telescopes, radio telescopes have reflectors and receivers Radio telescopes collect radio waves and send them to a receiver (4) Most radio telescopes need to be large in order to accommodate radio's longer wavelengths and lower energies Can “see” day or night

10. Problems with Optical Astronomy (6) Optical astronomers can only observe on clear, cloudless nights.(6) Also, optical astronomers can only work after dark, when stars are visible.(6) Radio wave data can be collected at almost any time, day or night.

11. Hubble Telescope Hubble orbits 600 kilometers (375 miles) above Earth, working around the clock to unlock the secrets of the Universe. It uses excellent pointing precision, powerful optics, and state-of- the-art instruments to provide stunning views of the Universe that cannot be made using ground-based telescopes or other satellites.

12. Hubble Images

13. The Very Large Telescope (VLT) Cerro Paranal, Chile Uses 4 separate large telescopes as well as several other small telescopes to create 1 large telescope. The large telescope mirrors are 8 meters across.

16. Arecibo (Puerto Rico) The main reflector is 1000 feet in diameter It can see 1/3 of the sky at a time

17. The Very Large Array (VLA) New Mexico The VLA is equivalent to a dish 22 miles across

18. The Spectroscope (8) The bands of colors that are produced when passed through a prism is called the visible spectrum. Astronomers use the bands of colors from distant stars to learn more about those stars. Spectroscope: tool used to separate starlight into its colors (8) Composed of a prism that separates the light and then the spectrum of colors is viewed with a tiny viewing telescope (8)

19. Why a Spectroscope? (8) The spectra viewed from this tool allows astronomers to determine which chemical elements are present in the star’s outer layers.(8) Indicates temperature, pressure, magnetic field, and condition of gases in the stars.(8) Allows astronomers to learn if the distance between Earth and the star is increasing or decreasing.(8) One of the most useful tools that astronomers have for learning about the universe.

20. Other Eyes X-Ray Infrared Gamma Ray

21. The Milky Way Galaxy Radio Infrared Visual X-Ray Gamma Ray

22. The End