Download Telescopes

Telescopes
Chapter 5
Objectives
Telescopes……………Chapter 5
Objectives:
 1. To list the parts of a telescope.
 2. To describe how mirrors aid in telescope
magnification.
 3. To describe three different types of
telescopes.
 4. To construct a simple telescope.
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What do you think of when someone
asks you about a telescope?
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Some of these terms should come to mind:
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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What are the two most important
properties of a telescope?
1.
2.
______________________________: Also
called Collecting Power. Telescopes with a
larger collecting area can gather a greater
amount of light in a shorter time.
_______________________________: Also
called Resolving Power. Telescopes that are
larger are capable of taking images with
greater detail.
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 (easier for you to see)
• This is the primary reason for making telescopes
larger.
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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.
• ___________________– 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 _______________ to focus light
 Are limited by the size and quality of
the lens.
 Most modern telescopes are
reflecting telescopes as opposed to
refracting telescopes.
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Focusing Light
Cameras
detect light
with chargecoupled
devices
(CCDs).
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A camera focuses light like an eye and captures the image
with a detector.
Because we can control the exposure time (amount of time
the light collects on the detector), a camera can record
details that are too faint to see with our eyes alone.
The CCD detectors in digital cameras are similar to those
used in modern telescopes.
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.
Reflecting telescopes
Use __________________ to collect
and focus light.
 Reflectors 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.
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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.
Interferometers
A device consisting of ____________
______________________ 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?
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Light Pollution
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___________________________ is city light
scattering off the atmosphere and into a telescope.
Scattering of human-made light in the atmosphere
is a growing problem for astronomy when using
land-based telescopes.
Why do we put telescopes into
space?
Benefits of Space Telescopes
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Only radio and visible light pass easily through
Earth’s atmosphere. We need telescopes in
space to observe other forms.
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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