Astronomy Chapter 3: Telescopes Answers – Flashcards
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"Adaptive optics " is a newer technology that has significantly improved the ability to collect good data at the telescope. What problem has been corrected by adaptive optics?
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turbulence in the Earth's atmosphere that creates twinkling
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A telescope's primary purpose is to
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collect a large amount of light and bring it into focus.
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Astronomers use the term _________________________ to describe the effects of atmospheric turbulence on the image that they collect with a telescope.
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"seeing"
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CCD detectors have several advantages in collecting light images at the telescope when compared to using the older technology of photographic film. The most important is that...
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they record much more light in a given exposure time.
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Compared to optical telescopes, radio telescopes are built larger mostly due to the fact that
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cosmic sources giving off radio waves are often very faint
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Galileo is credited with designing the first reflector telescope. (T or F)
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False
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In astronomy, an interferometer can be used to
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improve the angular resolution of radio telescopes.
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In terms of their design, refractors have certain disadvantages that are not present in reflecting telescopes. Which of the following is NOT a disadvantage in the design and use of refractors?
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Lenses are harder to focus than mirrors.
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It is diffraction that limits the ________ of a telescope of a given objective diameter.
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resolution
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Like radio and optical astronomy, infrared astronomy is easily done with ground-based telescopes. (T or F)
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False
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Nasmyth/Coude reflecting telescopes are used in astronomy primarily because
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they can easily accomodate a variety of cameras, instruments and other detection equipment
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One advantage of the Hubble Space telescope over ground based ones is that
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in orbit, it can operate close to its diffraction limit at visible wavelengths.
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Perhaps the greatest value of radio astronomy to developing our understanding of the universe is
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that it allows us to observe objects and events that would otherwise be hidden by intervening clouds of dust and gas (visible light and other waves can't get through)
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The Spitzer Space Telescope has made numerous important observations since its launch by NASA in 2003. Which part of the electromagnetic spectrum do its detectors predominantly study?
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Infrared
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The adaptive optics technology currently being developed for placement on the Hubble Space Telescope will greatly enhance its resolving power. (T or F)
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False
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The design of modern X-ray telescopes depends on
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grazing incidence optics.
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The light-gathering ability of a telescope is most dependent on the diameter of its primary objective/mirror. (T or F)
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True
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When light from a distant celestial object reflects off of a concave telescope mirror (bowl-shaped mirror), the reflected image will appear
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upside-down and reversed left-to-right
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The twin Keck telescopes on Mauna Kea have been used to make many discoveries since their commisioning back in the early 1990s. Which of the following is considered to be one of their most important?
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the discovery that the universe is expanding at an ever -accelerating rate
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Very long baseline interferometry (VLBI), using instruments spaced 1000's of kilometers apart, can acheive an image resolution in the microarcsecond (0.000001") range. (T or F)
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False
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What are the factors that determine a telescope's light-gathering ability?
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the exposure time and collecting area of the optics
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What is true of radio telescopes?
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They have poorer angular resolution than a refractor of the same size.
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When a light ray moves into an optically denser material at an angle to the boundary, as shown below, the light ray will...
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slow down slightly and bend towards the normal in the denser medium
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Which of the following would not be used as part of an 'active optics' system on a research telescope?
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the use of a permanent "corrector lens" system placed in the light path to sharpen the image of the primary mirror once it has been installed and tested
