Telescopes

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Telescopes Light Part 1
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A Telescopes is a tool used to gather light from
objects in the universe.
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There are two different types of telescopes

• A refracting telescope uses a glass lens to
  concentrate incoming light.
• A reflecting telescope uses mirrors to
  concentrate incoming starlight.

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Which of the following is the most important
feature of a telescope?

1. Ability to gather light.
2. Ability to see fine detail.
3. Ability to magnify the image.

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Three main functions of a telescope

• Most important!!
• Gather More Light (bigger Is better) making
  objects appear brighter
• followed by
• to see fine detail
• (called resolution)
• and least important,
• magnify
• magnification (objective lens focal length /
  eyepiece lens focal length)

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A larger objective lens provides a brighter (not
bigger) image
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If you pass white light through a prism, it
separates into its component colors.
long wavelengths
ROY G B I V
short wavelengths
spectrum
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But visible light is only one type of
electromagnetic radiation (light) emitted by stars
Astronomers are truly interested in the entire
spectrum of light!
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Consider Orion as Seen in Different Wavelengths
of light!
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Observations at other wavelengths are revealing
previously invisible sights
UV
Infrared
Map of Orion region
Ordinary visible
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Sun as seen in visible light from Earth (right)
and from space in X-rays by satellites (left)
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Radio wavelength observations are possible from
Earths surface
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The Very Large Array (VLA) in New Mexico
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Differences in the temperature and density of
small portions of Earths atmosphere cause
passing starlight to quickly change direction,
making stars appear to twinkle.
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Earths atmosphere hinders astronomical research
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High above Earths atmosphere, the Hubble Space
Telescope provides stunning details about the
universe
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Astronomers use different instruments to look at
light of different wavelengths - sometimes, we
even have to go above Earths atmosphere.
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Not all EM radiation can penetrate Earths
atmosphere.
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Tutorial Telescopes and Earths Atmosphere pg.
49

• Work with a partner!
• Read the instructions and questions carefully.
• Discuss the concepts and your answers with one
  another. Take time to understand it now!!!!
• Come to a consensus answer you both agree on.
• If you get stuck or are not sure of your answer,
  ask me or another group.

20
Which is the correct reasoning for why a gamma
ray telescope located in Antarctica that is to be
used to look for evidence of black holes in the
centers of galaxies would not get funded?

1. There is no way to detect the presence of a black
   hole.
2. Gamma rays are too energetic to detect with a
   telescope.
3. You cant build a functioning telescope in
   Antarctica.
4. Gamma rays dont penetrate Earths atmosphere.

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Imagine youre the head of a funding agency that
can afford to build only one telescope. Which of
the three proposed telescopes below would be best
to support?

1. A gamma ray telescope in Antarctica.
2. A radio telescope in orbit above the Earth.
3. A visible telescope located high on a mountain in
   Peru.
4. An ultraviolet telescope located in the Mojave
   desert.

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McDonald Observatory (Fort Davis, TX)
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A Few Astronomy Factoids (Or So You Think You
Want to be an Astronomer)

• Research quality images are monochromatic.
• Astronomy research is not the safest, but is much
  safer than it once was due to the use of CCDs
  over photographic plates.
• Astronomy research is time consuming and
  expensive.
• Astronomers spend more time in front of a
  computer than at a telescope.
• Professional astronomers rarely ever actually
  look through an eyepiece.