Download Telescopes

Telescopes
Chapter 5
What do you think of when someone
asks you about a telescope?
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Types of telescopes
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Interferometers (not a type of telescope, but
decrease light interference)
 Radio telescopes
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Telescopes
The most basic telescopes work by
gathering light, then focusing and/or
“bending light” onto a particular
spot.
 This causes an increase in the
magnification of an image.
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Determining a good telescope
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– how much more light that a
telescope can gather than the human eye.
The larger the lens, the more collecting
power.
• This allows for a brighter image
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(easier for you to see)
Telescopes are first described by the
diameter of its light collecting device (mirror
or lens)
Once light is collected then it must be
focused.
Determining a good telescope
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How light is focused
– Light is focused to form a
particular image using a lens.
• Relies on the process of
which is the
bending of light when it goes through different
media. Occurs because the speed of light changes
when it enters the lens.
• Refraction also spreads the light out. Results in
the colors of the rainbow.
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– The spreading of light or other
electromagnetic radiation into a spectrum.
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The light rays are bent when they go through
one media (air) and then another (glass)
Refracting Telescopes
Use lenses to focus light
 Are limited by the size and quality of
the lens.
 Most modern telescopes are
reflecting telescopes as opposed to
refracting telescopes.
 We will make a refracting telescope
in class this week.
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Reflecting telescopes
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Use reflectors to collect and focus light.
are slightly curved mirrors
Light does not go through them and as a
result is not dispersed.
Most telescopes today are reflecting
Multiple mirrors bounce the light around,
each time bending it slightly and thus
magnifying the image.
Atmospheric Refraction
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Occurs for objects viewed in the sky.
The gases of the atmosphere bend light
and change the appearance of an object
refraction makes the sun
look higher in the sky than it really is.
Atmospheric refraction is stronger closer
to the horizon. Causes the sun to look flat
as it sets.
Determining a good telescope
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Besides collecting light, telescopes also
allow us to discern objects as single large
object or several small individuals
– The ability of a telescope or
instrument to discern fine details. Larger
diameter telescopes have greater resolving
power than smaller ones.
• Resolving power is limited because light waves
can be diffracted.
• Diffraction –
• Diffraction limits the resolving power of a
telescope.
Interferometers
A device consisting of two or more
telescopes connected together to
work as a single instrument.
 Allow for a high resolving power, the
ability to see small scale features.
 Can be used to increase the power of
radio, infrared, and visible
wavelengths.
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Observatories
As far as telescopes discussed by the
groups, for the test, make sure to
look over the telescopes and
observatories discussed in the book.
 Remember that SEVERAL telescopes
are located in Hawaii (Mauna Kea)
 Why are so many telescopes in HI?
 Cleaner air, less pollution, and
relatively high elevation.
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Non optical telescopes
Most X rays and UV light is absorbed
by the atmosphere.
 Radio waves can penetrate the
atmosphere.
 Gamma ray telescopes measure
gamma rays that are released during
nuclear explosions.
 These explosions occur during stellar
evolution.
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