Optics and Telescopes Chapter 5 Survey of Astronomy [email protected] om astro1010-lee.com.
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Optics and Telescopes Chapter 5 Survey of Astronomy [email protected] om a s t r o 1 0 1 0 - l e e . c o m
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Transcript of Optics and Telescopes Chapter 5 Survey of Astronomy [email protected] om astro1010-lee.com.
OpticalRadioInfraredUltravioletX-RayGamma Ray
Telescopes have been developed for every portion of the Electro-Magnetic Spectrum
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Optics and Telescopes
Telescopes on Mauna Kea
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Early Optical Telescopes use the Refraction property of waves to collect and focus light
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A Refractor or Refracting Telescope
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One of several difficulties with a lens is that it is a prism and colors bend at different rates. Another is that it is extremely difficult to obtain a large piece of glass that is of telescope quality.
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Modern telescopes use the Reflective property of waves to gather and focus light. By correctly curving the mirror into a parabaloid shape light can be collected and focused.
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There are several basic mounts for Reflector telescopes that have been invented. Some of them are shown below.
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Film has been replaced. Now data is digitized directly using a CCD (Charge Coupled Device). These, too, are becoming more and more sophisticated.
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Larger telescopes are desirable to attain better resolution. The image (a) was obtained with a telescope twice the size of the telescope that took image (b)
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Atmospheric blurring is often due to air movements. In the past this has limited the size of Earth based telescopes. Solutions have included telescopes on mountain tops and active optics.
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The best solution to date has been Adaptive Optics that track atmospheric changes with a laser then adjust the shape of the mirror in real time to compensate.
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The Earth’s Atmosphere effectively blocks most radiation from space. There is a window for visible light and a rather large window in the radio wavelengths that can be accessed from the ground. There are few infrared wavelengths that can be accessed from high mountains and high flying airplanes. The rest of the wavelengths can only be seen in space.
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Much information can be obtained from Earth based Radio Telescopes using the radio window.
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Radio telescopes are similar to optical reflecting telescopes but are less sensitive to imperfections in the receiver (due to the longer wavelengths) and they can be made very large
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This is called the Very Large Array. It samples very long radio waves. This large array has the resolution of a telescope as large as the longest distance between dishes. Signals are welded together by interferometry as if they were coming from a single instrument.
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Before adaptive optics and before the advent of the large land based optical telescopes, the Hubble Space Telescope was launched into orbit. It amazed the community. It is still doing an excellent job even as old as it is. The new scopes now are passing it by and they need much less expensive maintenance.
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Infrared Ultraviolet X-Ray
Gamma Ray
These are a few of the fleet of telescopes that now cover the wavelengths that can not be seen from the surface of the Earth.
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Much can be learned from observing the same astronomical object at many wavelengths. Here is the Milky Way in several wavelengths.
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