1. January 24, 2006Astronomy 20101 Chapter 5 Astronomical Instruments How do we learn about objects too far away for spacecraft? How do telescopes work? Do all telescopes use light? Why are telescopes located on mountains? Why are some telescopes in orbit around the Earth?

2. January 24, 2006Astronomy 20102 5.1 Telescopes Telescopes are devices for “seeing” distant objects. –To see faint objects, collect more light by using a bigger aperture. –Magnification is much, much less important. Two types of optical telescopes: –Refracting –Reflecting

3. January 24, 2006Astronomy 20103 Refracting Telescopes Use a large lens as the primary light collecting element. Common in older telescopes. Chromatic aberrations and ultraviolet cutoff.

4. January 24, 2006Astronomy 20104

5. January 24, 2006Astronomy 20105 Reflecting Telescopes Use a large mirror as the primary light collecting element. Easier to make a large mirror than a large lens. Modern telescopes are reflectors. Reduced chromaticity problems.

6. January 24, 2006Astronomy 20106 Refracting versus Reflecting

7. January 24, 2006Astronomy 20107 Prime, Newton, and Cassegrain

8. January 24, 2006Astronomy 20108 5.2 Optical Detectors and Instruments Second greatest advance in astronomy was the use of photographic film –Longer integration time than the eye. –Images available for later (re)inspection. The 3 uses of telescopes: –Imaging –Measuring brightness and color –Spectroscopy All benefit from longer integration time.

9. January 24, 2006Astronomy 20109 Charge-Coupled Device A modern advance is the use of charge- coupled devices or CCD’s. These are the “digital film” of digital cameras.

10. January 24, 2006Astronomy 201010 5.3 Optical and Infrared Observatories Ground based telescopes are housed in domes or other structures to protect them when not in use. They are often located on remote mountains, away from lights, and smog, and above humid and turbulent air.

11. January 24, 2006Astronomy 201011 NOAO on Kitt Peak, AZ

12. January 24, 2006Astronomy 201012 South African Large Telescope

13. January 24, 2006Astronomy 201013 European Southern Observatory

14. January 24, 2006Astronomy 201014 Choice of Telescope Sites Weather: clouds, wind, and rain limit observing time. Water vapor: water vapor in the atmosphere filters out infrared wavelengths. Darkness: city light can overwhelm faint stars. Turbulence: turbulent air blurs images.

15. January 24, 2006Astronomy 201015 Observatory Sites Newest telescopes are sited in the Chilean Andes, desert peaks of Arizona, Canary Islands, and Mauna Kea in Hawaii. Modern telescopes can use segmented mirrors, adaptive optics, and interferometry.

16. January 24, 2006Astronomy 201016 Observing Other Radiation To learn the most about planets, stars, and galaxies, astronomers use as many types of radiations as possible. –Radio –Infrared and ultraviolet –X-rays –Gamma rays

17. January 24, 2006Astronomy 201017 5.4 Radio Telescopes Many objects emit radio waves, from long wave to microwaves. Radio telescopes generally look like large satellite dishes. They can operate during the day and night. Large facilities in Puerto Rico, West Virginia, and New Mexico.

18. January 24, 2006Astronomy 201018

19. January 24, 2006Astronomy 201019 The Very Large Array (VLA)

20. January 24, 2006Astronomy 201020 The VLBA Spans A Continent

21. January 24, 2006Astronomy 201021 Radio Image of Quasar Jets

22. January 24, 2006Astronomy 201022 5.5 Observatories Outside the Earth’s Atmosphere Some wavelengths of radiation are absorbed by Earth’s atmosphere (gamma rays, x-rays, and ultraviolet). Telescopes for these wavelengths must be put in space. The Hubble telescope demonstrates the advantages for an optical telescope to be above the atmosphere.

23. January 24, 2006Astronomy 201023 The Hubble Space Telescope

24. January 24, 2006Astronomy 201024 The Swift Satellite (GRB’s)