1. Chapter 5
Telescopes

2. Chapter 5- Telescopes Outline
5.1- Optical Telescopes
5.2- Telescope Size
5.3- High-resolution Astronomy
5.4- Radio Astronomy
5.5- Interferometry
5.6- Other Astronomies
5.7- Full-Spectrum Coverage

3. 5.1 Optical Telescopes
Reflecting telescopes- a curved mirror is used to gather and concentrate a beam of light
Refracting telescope- a lens is used to focus the incoming light

4. 5.1 Optical Telescopes
Light does not pass through large lenses uniformly, causing the lens to focus the blue and red light differently- effecting the image of the star- chromatic aberration

5. 5.2 Telescope Size
Astronomers generally prefer large telescopes over small ones
The larger the telescope the greater the amount of light that can enter
More detail can be seen with the resolving power of a large telescope

6. Currently, the largest optical telescopes are the twin Keck telescopes on top of Mauna Kea in Hawaii
5.2 Telescope Size

7. 5.3 High-Resolution Technology
Photographic equipment for data acquisition is being replaced by CCDs- charge-coupled devices- electronic detectors that relay information directly to a computer using pixels to construct images

8. 5.3 High Resolution Technology
Active optics- techniques used to increase the resolution of ground-based telescopes
Minute modifications are made to the overall configuration of an instrument as its temperature and orientation change, to maintain the best focus and picture at all times

9. 5.4 Radio Astronomy
Radio telescopes- similar to optical reflecting telescopes, but are generally larger

10. 5.4 Radio Astronomy Radio telescopes are larger because:
The radio waves reaching Earth from space in tiny compared to other wavelengths
The long wavelengths of radio waves mean that diffraction severely limits the resolution unless a large instrument is used

11. Radio telescopes can be used 24 hours a day because they do not require light and are not effected by cloudy skies
5.4 Radio Astronomy

12. 5.4 Radio Astronomy
The greatest value of radio telescopes is that objects that are bright in the visible spectrum are not necessarily strong radio emitters and visible light may be strongly absorbed by interstellar dust along the sight to the source

13. 5.5 Interferometry
Interferometry- two or more radio telescopes are used in tandem to observe the same object at the same wavelength and at the same time- improving the angular resolution issue of radio telescopes

14. Infrared telescopes- similar to optical telescopes, but they detect longer wavelength radiation
5.6 Other Astronomies
IRAS- (infrared astronomy satellite)- has contributed to our knowledge of clouds of galactic matter destined to become stars

15. 5.6 Other Astronomies
Ultraviolet telescope- captures and analyzes high- frequency radiation
International Ultraviolet Explorer (IUE) captured images of supernova usually harder to see in detail due to extreme heat

16. 5.6 Other Astronomies
High-energy telescope- x- rays and gamma rays- types of radiation whose photons have the high frequencies and greatest energy