Astronomy ch 5
What are two advantages of large scopes over smaller ones?
Large telescope have more light grasp and better resolution.
What is the resolution of a telescope?
its ability to distinguish two adjacent objects close together in the sky
The Arecibo radio telescope is laid out like which optical telescope design?
prime focus reflector
This design involves only one optical surface, a concave mirror.
prime focus reflector
Which type of telescope has the simplest light path?
prime focus reflector
Which design is subject to chromatic aberration?
refractor
It is diffraction that limits the ________ of a telescope of a given objective diameter.
resolution
It is diffraction that limits the ________ of a telescope's objective.
resolution
Diffraction is the tendency of light to
spread around corners.
What is the resolving power of the telescope?
the ability to distinguish adjacent objects in the sky
What problem is adaptive optics designed to correct?
the effects of atmospheric turbulence
The amount of diffraction and thus the resolution of the scope depends upon
the wavelength used and the size of the main telescope objective lens or mirror.
The most important advantage of CCDs over film is that
they record much more light in a given exposure time
What problem does adaptive optics correct?
turbulence in the earth's atmosphere which creates twinkling
Which of these devices helps correct coma in fast reflectors?
Schmidt corrector plate
A mountain top is an especially good site for infrared telescopes since
-there you are closer to celestial objects. -less air above means better seeing in many cases. -the cold weather helps the sensitivity of infrared detectors. -you are above most of the carbon dioxide and water vapor in the atmosphere.
A telescope with a 60 mm objective lens collects how many times as much light as does your eye's 6 mm exit pupil?
100X
How much better resolution would a 60 mm objective lens have than your eye's 6 mm exit pupil?
10X
The angular resolution of an 8 inch diameter telescope is ________ greater than that of a 2-inch diameter telescope.
4×
What is the light-gathering power of an 8 inch telescope compared to a 4-inch telescope?
4× better
Why is the image seen in astronomical telescope eyepieces inverted?
As the eyepiece must lie behind the objective's focus, the light reaching it has already been flipped over once it passed the focal point.
The convex secondary mirror in this design focuses light down through a hole cut in the concave primary mirror.
Cassegrain reflector
Which of the following is currently supplying high resolution X-ray images from space?
Chandra
What are some advantages of radio telescopes over optical scopes?
Radio telescopes can be used day or night, they are much less affected by cloudy skies, and they open a new window to observe the Universe. They allow us to observe astronomical objects at a different wavelength than an optical telescope, thus giving an opportunity to compare and contrast the images.
Which of the following is a problem inherent in all large radio telescopes?
Radio waves have long wavelengths, so radio telescopes have poor resolution
Compare how doubling the diameter of a mirror will effect both resolution and light grasp.
The resolution would now be twice as sharp, but the increase in surface area, with the squaring for the area, would now detect stars four times fainter than before.
What is the primary purpose of an astronomical telescope?
To collect a lot of light and bring it to a focus.
What type of telescope is the Hubble Space Telescope?
cassegrain
Refractor telescopes suffer from this separation of light into its component colors.
chromatic aberration
What problem do refractor telescopes have that reflectors don't?
chromatic aberration
This design combines the radiation from two different telescopes to greatly enhance resolution via computer synthesis.
interferometer
The design of modern X-ray telescopes depends on
grazing incidence optics
One advantage of the Hubble Space telescope over ground based ones is that
in orbit, it can operate close to its diffraction limit at visible wavelengths.
