question

List 3 advantages of reflecting telescopes over refracting telescopes

answer

- the lens in a refracting telescope focuses red and blue light differently. This deficiency is known as chromatic aberration. - As light passes through the lens, some of it is absorbed by the glass. - A large lens can be quite heavy therefore it tends to deform by its weight. - A lens has two surfaces that must be accurately machined and polished, which can be a difficult task. A mirror has only one surface

question

How does earths atmosphere affect what is seen through an optical telescope

answer

Atmospheric turbulence produces continuous small changes in the optical properties of the air between the star and our telescope (or eye). The light from the star is refracted slightly, again and again, and the stellar image dances around on the detector (or retina).

question

what are the largest optical telescopes used today?

answer

Currently, the largest (and highest) optical telescopes are the twin Keck instruments atop Mauna Kea in Hawaii operated jointly by the California Institute of Technology and the University of California.

question

What advantages does the hubble space telescope have over ground base telescopes.

answer

A telescope placed above the atmosphere, in Earth orbit, can achieve resolution close to the diffraction limit. It has a 2.4-m mirror and a diffraction limit of 0.05", giving astronomers a view of the universe as much as 20 times sharper than that normally available from even much larger ground-based instruments.

question

What are the advantages of a CCD over a photograph?

answer

More Efficient and Digital Format CCDs are much more efficient than photographic plates, recording as many as 75 percent of the photons striking them, compared with less than five percent for photographic methods. CCDs produce a faithful representation of an image in a digital format that can be placed directly on magnetic tape or disk, or even sent across a computer network to an observer's home institution for analysis

question

Why do radio telescopes have to be very large?

answer

because the radio waves they are picking up are very large.

question

What is interferometry and what problem in radio astronomy does it address

answer

It is the combination of telescopes that are far apart to get a picture. The downside is the image quality is poor.

question

Compare the highest resolution attainable with optical telescopes to the highest resolution attainable with radio telescopes

answer

optical- level .1 arc second radio- 10 arc minute (w/o interferometry) but using it you can get to .1 arc second

question

What special conditions are required to conduct observations in the infrared?

answer

For most infrared observations, astronomers must place their instruments above most or all of Earth's atmosphere.

question

What are the main advantages of studying objects at many different wave lengths?

answer

By comparing the features visible in each, multi-wavelength observations can COMPLEMENT each other, greatly extending our perception of the universe around us.

question

The main advantage of the HST is the increased amount of nighttime viewing it affords (T/F)

answer

F

question

The term "seeing" is used to describe how faint an object can be detected by a telescope (T/F)

answer

F

question

One of the primary advantages of CCD's over photographic plates is the formers high efficiency in detecting light (T/F)

answer

T

question

Radio telescopes are large in part to improve their angular resolution which is poor because of the long wavelengths at which they are used to observe the skies (T/F)

answer

T

question

Infrared astronomy can only be done from space (T/F)

answer

F

question

Gamma-ray telescopes employ the same basic design that optical instruments use (T/F)

answer

F

question

Because gamma rays have very short wavelengths, gamma ray telescopes can achieve extremely high angular resolution (T/F)

answer

F

question

The main reason that most professional research telescopes are reflectors is that _______?

answer

large mirrors are easier to build than large lenses

question

If telescope mirrors could be made in odd sizes, the one with the most light gathering power would be a triangle with 1-m sides; a square with 1-m sides;a circle with 1-m diameter;or a rectangle with two 1-m sides and two 2-m sides?

answer

Rectangle that's 1 by 2

question

The primary reason professional observatories are built on the highest mountaintops is to ______?

answer

Reduces atmospheric blurring

question

When multiple radio telescopes are used for interferometry, resolving power is most improved by increasing ______?

answer

the distance between telescopes

question

The Spitzer Space Telescope is stationed far from earth because it _____?

answer

Earth is a heat source and the telescope must be kept very cold

question

The best way to study young stars hidden behind interstellar dust clouds would be to use_______?

answer

Infrared light

question

optical telescope

answer

the most common type of telescope that collects and focuses visible light for closer observation. The simplest optical telescope contains an objective lens and a lens in the eyepiece of the telescope

question

refracting telescope

answer

uses lenses to gatehr and focus light. Cannot focus images perfectly, distorts images if lens is too large

question

reflecting telescope

answer

uses mirrors to gather and focus light. I sused by most professional astronomers. Focuses all colors of light to the same focal point, can use large mirrors to gather light and flaws in the glass don't affect the collected light

question

2 disadvantages of refracting telescopes

answer

their lenses focus different colors of light at different distances, which means the images cannot be exactly focused. Second, if the objective lens is too big, it will sag and images will be distorted

question

3 advantages of reflecting telescopes

answer

1. mirrors can be large, which allows reflecting telescopes to gather much light. 2. they use mirrors and light doesn't eneter the glass, so any damages in the glass don't distort the image. 3. their mirrors focus all colors of light to the same focal point so all colors of light from and abject can be seen and focused.

question

Blocked wavelengths from earth

answer

infrared rays, and X-rays

question

unblocked wavelengths from earth

answer

gamma rays, visible light, microwaves

question

Radio telescopes

answer

are larger than optical telescopes because radio wavelengths are much longer than optical wavelengths. The surface can also be more flawed than the lenses and mirrors of an optical telescope

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