Non-optical telescopes

Question 1

What is collecting power of a telescope proportional to?

Answer 1

collecting area or diameter squared

Question 2

What does is it the collecting area of?

Answer 2

Objective mirror/dish

For UV it is the size of the opening through which the X-Rays can enter

Question 3

Do X-Ray telescopes have higher or lower collecting power than other Telescopes?

Answer 3

lower

Question 4

Why does a bigger dish mean better collecting power?

Answer 4

Collects more energy in a given time. This means a more intense image

Question 5

Higher collecting power means a more intense image, so the telescope can observe ……… objects

Answer 5

fainter

Question 6

In what ways are radio telescopes similar and differences to optical telescopes??

Answer 6

Parabolic dish works the same as objective mirror of a optical reflecting telescope
Antenna used as detector at the principal focus instead of eye
Manoeuvrable
No equivalent to the eye lens of an optical telescope

Question 7

What is the order of the components of a Radio telescope?

Answer 7

Question 8

1) What does a preamplifier do?

Answer 8

Amplifies weak radio signals without adding too much noise to the signal

Question 9

2) What does the second amplifier do (High-Gain amplifier)?

Answer 9

The signal is amplified further.

Question 10

3) What does the filter do?

Answer 10

Filter out any unwanted wavelengths.

Question 11

4) What does the computer create? How does it create it?

Answer 11

A computer creates a “false-colour image” of the detected radio signals. Different colours are assigned to different wavelengths or intensities to produce “false-colour images” of non-visible EM radiation.

Question 12

How is the source stopped from slipping out of view of the radio telescope?

Answer 12

Question 13

How big are radio waves compared to light?

Answer 13

About a million times longer

Question 14

How big would a radio telescope need to be to have the same resolving power as an optical telescope?
How do scientists get around this?

Answer 14

A million times bigger

Linking lots of them together, data is combined to form a single image

Question 15

What is used in a radio telescope instead of the polished mirror of an optical telescope?

Answer 15

Wire mesh

Question 16

What advantages are there of using wire mesh?

Answer 16

Construction is cheaper and easier, dish doesn’t need to be as perfect because the longer wavelength radiation of radio waves is less affected by imperfections.

Question 17

Why does the dish shape of a radio telescope have to have a precision of λ/20 ?

Answer 17

To avoid spherical aberration

Question 18

What is the biggest problem with doing astronomy on earth?

Answer 18

Atmosphere stops certain wavelengths from coming through

Question 19

What 2 waves can be observed on the surface of the earth?

Answer 19

Optical ( a little UV and a little IR)

Radio

Question 20

What happens to the most of the IR radiation that gets through the atmosphere?

Answer 20

Absorbed by water vapour

Question 21

Where is the best place to observe infrared radiation?

Answer 21

High and dry places E.G The Mauna Kea volcano in Hawaii

Question 22

How do you detect X-rays and Ultra violet radiation?

Answer 22

Strap the UV and X-Ray telescopes to high-altitude weather balloons or aeroplanes

Question 23

Where is the ideal place to put your telescope?

Answer 23

In space

Question 24

How are IR and UV telescopes similar to optical reflecting telescopes?

Answer 24

Use the same parabolic mirror

Question 25

What’s the same about UV and IR telescopes?

Answer 25

Both use CCDs as radiation detectors

And both use parabolic mirrors

Question 26

The longer the wave length the ….. its effected by imperfections

Answer 26

Less

Question 27

How precise does the mirror shape in IR and Radio telescopes need to be and why?

Answer 27

Not as precise

Because it’s has a long wavelength so is affected less by imperfections

Question 28

How precise does the mirror shape in UV telescopes need to be?

Answer 28

More precise

Because it’s has a shorter wavelength so is affected more by imperfections

Question 29

What’s the problem with IR telescopes that does effect any other type of telescope?

Answer 29

It creates its own infrared radiation so needs to be cooled to very low temperature using liquid helium or refrigeration units

Question 30

What’s different about X-Rays compared to other EM radiation?

Answer 30

Don’t reflect of surfaces.

They are usually either absorbed or pass straight through it

Question 31

When do X-Rays reflect?

Answer 31

If they just graze a mirror surface

Question 32

Explain how a grazing telescope works

Answer 32

A series of nested mirrors to gradually change the direction of X-Rays to bring them to focus on a detector

Question 33

What are X-Rays detected by?

Answer 33

Modified Geiger counter or fine wire mesh, modern X-Ray telescopes use highly sensitive CCD cameras.