Astronomy Ch 5

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

photometry

The primary purpose of a telescope is to

collect a large amount of light and bring it into focus

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

refraction

Compared to optical telescopes, radio telescopes are built large because

radio photons don’t carry much energy

The amount of diffraction a telescope creates depends upon:

the wavelength and the diameter of the telescope objective

What is the resolution of a telescope?

its ability to distinguish two adjacent objects close together in the sky

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

We now can access information in all spectral lengths

What problem is adaptive optics designed to correct?

the effects of atmospheric turbulence

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

use of interferometers

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

resolution

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

resolution

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

In astronomy, an interferometer can be used to

improve the angular resolution of radio telescopes

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

Cassegrain reflector

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

What is true of radio telescopes?

They have poorer angular resolution than a refractor.

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

All of the above are factors

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

Cassegrain reflector

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

Chandra

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

prime focus reflector

What is the primary purpose of an astronomical telescope?

To collect a lot of light and bring it to a focus

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

4x better

What is the resolving power of the telescope?

the ability to distinguish adjacent objects in the sky

A major advantage of a Newtonian reflector over a refractor is

the elimination of chromatic aberration

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

10x

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

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

Why are most large telescopes reflectors, not refractors?

All of the above

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

chromatic aberration

The design of modern x-ray telescopes depends on

grazing incidence optics

Which of these devices helps correct coma in fast reflectors?

Schmidt corrector plate

Diffraction is the tendency of light to

spread around corners

Radio dishes are large in order to:

increase their angular resolution and collect the very weak radio photons.

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

reflection

What are two advantages of large scopes over smaller ones?

Large telescopes have more light grasp and better resolution

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

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

chromatic aberration

Which type of telescope has the simplest light path?

prime focus reflector

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

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

have the same light gathering power

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

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

4x

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

provide better angular resolution than orange light

The most important advantage of CCDs over film is that

they record much more light in a given exposure time

What is "seeing"?

a measurement of the image quality due to air stability

What problem does adaptive optics correct?

turbulence in the earth’s atmosphere which creates twinkling

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

prime focus reflector

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

interferometer

What type of telescope is the Hubble Space Telescope?

cassegrain

Which design is subject to chromatic aberration?

refractor

*Essay: 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.