Lecture 7

Question 1

how does the earth’s atmosphere affect resolution of a telescope? what is the solution to this?

Answer 1

it blurs out images

therefore, resolution is higher when the telescope is above the atmosphere

Question 2

how does the hubble space telescope have such good imaging despite being a relatively small telescope size?

Answer 2

it is above the earth’s atmosphere

Question 3

what happens to light around sharp edges?

Answer 3

it diffracts

this limits sharpness of images or their resolution

Question 4

define the diffraction limit of a telescope

what does it depend on?

what unit is it measured in?

Answer 4

the minimum angle it can resolve

depends on (lambda) wavelength of the light and (D) diameter of the telescope aperture

measured in arcseconds

Question 5

compare what well solved and not resolved looks like

Answer 5

well resolved stars: looks like two points of light

not resolved looks like one point of light

Question 6

a larger telescope aperture (D) improves _____

Answer 6

resolution

Question 7

what are CCDs?

Answer 7

charge coupled devices

• can convert photons to electrons to produce electrical current
• very light sensitive
• easy to digitize, store and manipulate
• used in video cameras and cell phones

Question 8

describe radio telescopes

Answer 8

collects radio waves from stars, nebulae, galaxies

- like large satellite dishes which focus waves to antenna (the detector which converts signal to electric current)

Question 9

what is radio interference?

Answer 9

caused by proliferation of radio transmitting devices on earth (eg cell phones) adn in orbit (GPS)

Question 10

what is aperture synthesis

Answer 10

total collecting area sum of the collecting areas of individual telescopes

but also results in the resolution of a very large telescope

produces beautiful radio images, but with false colors which were chosen to represent wavelengths of radiation or intensity of radiowaves