January 24, 2006Astronomy 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?

January 24, 2006Astronomy 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

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

January 24, 2006Astronomy 20104

January 24, 2006Astronomy 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.

January 24, 2006Astronomy Refracting versus Reflecting

January 24, 2006Astronomy Prime, Newton, and Cassegrain

January 24, 2006Astronomy 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.

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

January 24, 2006Astronomy 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.

January 24, 2006Astronomy NOAO on Kitt Peak, AZ

January 24, 2006Astronomy South African Large Telescope

January 24, 2006Astronomy European Southern Observatory

January 24, 2006Astronomy 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.

January 24, 2006Astronomy 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.

January 24, 2006Astronomy 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

January 24, 2006Astronomy 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.

January 24, 2006Astronomy

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

January 24, 2006Astronomy The VLBA Spans A Continent

January 24, 2006Astronomy Radio Image of Quasar Jets

January 24, 2006Astronomy 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.

January 24, 2006Astronomy The Hubble Space Telescope

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