Astronomy Chapter 5

What are two advantages of large scopes over smaller ones?

Large telescope have more light grasp and better resolution.

This design involves only one optical surface, a concave mirror.

prime focus reflector

Which of these devices helps correct coma in fast reflectors?

Schmidt corrector plate

The primary purpose of a telescope is to

collect a large amount of light and bring it into focus.

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

Why are most large telescopes reflectors, not refractors?

All of the above are correct

Diffraction is the tendency of light to:

spread around corners

A major advantage of a Newtonian reflector over a refractor is

the elimination of chromatic aberration

What problem is adaptive optics designed to correct?

the effects of atmospheric turbulence

Green light has a shorter wavelength than orange light. In a 5 inch telescope, green light will

provide better angular resolution than orange light.

In astronomy, an interferometer can be used to

improve the angular resolution of radio telescopes

Which of the following greatly improves the angular resolution of radio maps?

use of interferometers

The most important advantage of CCDs over film is that

they record much more light in a given exposure time.

What is the resolving power of the telescope?

the ability to distinguish adjacent objects in the sky

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.

Describe at least three advantages of CCD imaging over visual or photographic work.

The CCD is far more efficient in capturing light than the fastest film, so fainter objects can be imaged with much shorter exposures or with smaller, cheaper telescopes. The image is digital, and can be monitored as it is building up for quality assurance; you don’t have to wait to develop the film to know that you have good data. This digital image is easily stored on computers, and quickly shared with others via the Internet and many other media.

Which of the following is a problem inherent in all large radio telescopes?

Radio waves have long wavelengths, so radio telescopes have poor resolution.

Which method of astronomical measurement is the precise measurement of brightness?

photometry

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.

It is diffraction that limits the ________ of a telescope of a given objective diameter.

resolution

In which part of the electromagnetic spectrum have astronomers been unable to get any information?

We now can access information in all spectral lengths

It is diffraction that limits the ________ of a telescope’s objective.

resolution

The amount of diffraction a telescope creates depends upon:

the wavelength and the diameter of the telescope objective.

The angular resolution of an 8 inch diameter telescope is ________ greater than that of a 2-inch diameter telescope.

4x

What problem does adaptive optics correct?

turbulence in the earth’s atmosphere which creates twinkling

Which type of telescope has the simplest light path?

prime focus reflector

How much better resolution would a 60 mm objective lens have than your eye’s 6 mm exit pupil?

10x

What is "seeing"?

a measurement of the image quality due to air stability

How do radio interferometers greatly enhance resolution in radio wavelengths?

Hooking two or more radio dishes together with a computer lets us get resolution not equal to the diameters of the dishes, but to the separations between the scopes.

The name of the new Infrared Orbiting Observatory is the:

Spitzer Space telescope

The angular resolution of an 8 inch diameter telescope is ________ greater than that of a 2-inch diameter telescope.

4x

What problem do refractor telescopes have that reflectors don’t?

chromatic aberration

Compared to a 5 inch prime focus reflector, a 5-inch Newtonian reflector will

have the same light gathering power.

What type of telescope is the Subaru telescope (shown below)?

Cassegrain reflector

What is the primary purpose of an astronomical telescope?

collecting light and bring it to focus

The process occurring when photons bounce off a polished
surface is called:

reflection

Which design is subject to chromatic aberration

prime focus reflector

The tendency of a wave to bend as it passes from one
transparent medium to another is called:

refraction

The primary purpose of a telescope is to

A) collect a large amount of light and bring it into focus. B) magnify distant objects.

This design involves only one optical surface, a concave mirror.

prime focus reflector

Why are most large telescopes reflectors, not refractors

Large lenses deform under their own weight, but mirrors can be supported. B) Large mirrors need only one optical surface, achromats four surfaces to grind. C) Reflectors do not suffer from chromatic aberration like refractors do. D) Large, very clear lenses are harder to cast than more tolerant mirror blanks

Which design has a convex primary mirror and flat secondary
mirror, with the eyepiece located on the top side of the telescope
tube?

Newtonian reflector

The convex secondary mirror in this design focuses light down
through a hole cut in the concave primary mirror

Cassegrain reflector

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 angular resolution of an 8 inch diameter telescope
is _______ greater than that of a 2 inch diameter telescope

4−times

It is diffraction that limits the ________ of a telescope’s:

angular resolution

What is the (angular) resolution of a telescope?

its ability to see very faint objects

What is the resolving power of the telescope

the ability to distinguish adjacent objects in the sky

What is the light−gathering power of an 8 inch telescope compared
to a 4 inch telescope

4−times better

Compared to a 5 inch prime focus reflector, a 5 inch Newtonian
reflector will

have the same light gathering power.

Which method of astronomical measurement is the precise
measurement of brightness

photometry

A telescope with a 60 mm objective lens collects how many times
more light than does your eye’s 6 mm pupil

100X

Diffraction is the tendency of light to:

spread around corners.

It is diffraction that limits the ________ of a telescope
of a given objective diameter.

angular resolution

What are two advantages of large telescopes over smaller ones?

Large telescope have more light grasp and better angular resolution

The amount of diffraction a telescope creates depends upon

the wavelength and the diameter of the telescope objective

What type of telescope is the Hubble Space Telescope

refractor OR cassegrain

Refractor telescopes suffer from this separation of light
into its component colors

chromatic aberration

One advantage of the Hubble Space telescope over ground
based telescopes is that

its adaptive optics controls atmospheric blurring better.

Green light has a shorter wavelength than orange light.
In a 5 inch telescope, green light will

provide better angular resolution than orange ligh

What is "seeing"?

a measurement of the image quality due to air quality

A mountain top is an especially good site for infrared telescopes since:

you are above most of the carbon dioxide and water vapor in the atmosphere

What problem does adaptive optics correct?

turbulence in the earthʹs atmosphere which creates twinkling

What problem is adaptive optics designed to correct

the effects of atmospheric turbulence

The Arecibo radio telescope is laid out like which optical
telescope design?

prime focus reflector

What is true of radio telescopes?

They have poorer angular resolution than an optical refractor.

Which of the following is a problem inherent in all large radio telescopes

Radio waves have long wavelengths, so radio telescopes have poor angular resolution.

Radio dishes are large in order to:

increase their angular resolution and collect the very weak radio photons

36) In astronomy, an interferometer can be used to

improve the angular resolution of radio telescope

This design combines the radiation from two different telescopes
to greatly enhance angular resolution via computer synthesis

interferometer

Which of the following greatly improves the angular resolution
of radio maps

use of interferometers

In which part of the electromagnetic spectrum have astronomers
been unable to get any information?

We now can access information in all spectral lengths

Which of the following is currently supplying high resolution
x−ray images from space?

Chandra

The design of modern x−ray telescopes depends on

grazing incidence optics

The name of the new Infrared Orbiting Observatory is the

Spitzer Space Telescope.

The Chandra X−ray telescope must use:

grazing incidence optics to focus the short wavelengths