Unit 3 (Telescopes): "Telescopes & Spectroscopy"

Question 1

Why is building Telescopes on Mountains beneficial?

Answer 1

There’s less air to see through.

Question 2

What is an aperture and what does it do?

Answer 2

A hole in the lens that controls how much light gets into the telescope

Question 3

Chromatic Aberration is primarily a problem for which type of telescope?

Answer 3

Refracting Telescopes

Question 4

What is Chromatic Aberration?

Answer 4

A color distortion = an outline of unwanted color along an object edge

Question 5

How can you reduce Chromatic Aberration?

Answer 5

Using an achromatic lens; puts focal points in the same location) OR use a longer tube.

Question 6

What types of telescopes are ground-based? What types are space-based?

Answer 6

Ground-based = reflecting &
Space-based = refracting

Question 7

What is the difference between an emission spectrum and an absorption spectrum?

Answer 7

An emission spectrum = colored lines;
Absorption spectrum = dark-colored lines

Question 8

What are some uses of spectroscopy?

Answer 8

Determines how each type of molecule/ atom will reflect, absorb, or emit electromagnetic radiation.

Question 9

Reflecting Telescope Pros

Answer 9

• Easy construction; affordable
• No occlusions (light passes through)
• Light wavelengths are equally reflected
• Can be created largely in size & durable (the larger = more light accessible to eye piece)

Question 10

Do all elements have the same emission spectrum?

Answer 10

No; different numbers of protons & arrangements of electrons.

Question 11

Reflecting Telescope Cons

Answer 11

• Periodic mirror cleaning
• Mirror must be realigned after cleaning (expensive)
• Improper alignment = blurry images
• Periodic mirror polishing (tarnished due to air exposure)

Question 12

What is spectroscopy?

Answer 12

• Using radiation in an object for information on its structure & properties of matter.
  (The study of the absorption, emission of light, and other radiation by matter)

Question 13

Refracting Telescope Pros

Answer 13

• Easy to use & more reliable due to permanently fixed optics.
• Resistant to misalignment
• Glass surface within tube rarely needs cleaning (sealed from the atmosphere)
• Air currents + effects from changing temperatures are eliminated (clear image given)

Question 14

True or False: All elements have unique, distinct spectral lines.

Answer 14

True

Question 15

What does diffraction grating do?

Answer 15

An optical element that divides light composed of different wavelengths into light components by wavelength

Question 16

Refracting Telescope Cons

Answer 16

• Heavy (large lenses)
• Concern for transportation (large size)
• Expensive
• Technically difficult to shape glass lenses without imperfections inside
• Due to the thickness of the lens, the quality of light passing through the objective varies.
• Experiences “spherical aberration” (light is not focused at the same point)

Question 17

Hybrid Telescope Pros

Answer 17

• “Catadioptric” telescopes use a folded-path optical system and thus can be shorter than their focal length would imply.
• They are lighter and more compact, as is the mount that holds them.
• Convenient transportation = mechanical size and reduced weight.
• The ability to use mirrors with spherical figures
• Easily reproduced refractive elements, usually called corrector lenses = lower manufacturing costs.

Question 18

Hybrid Telescope Cons

Answer 18

• Become heavy quickly; increase in aperture.
• May require more frequent optical alignment
• A “catadioptric” telescope’s moving parts are complex
• Have an inherent optical performance limitation based on the central obscuration of their aperture caused by their own secondary mirror. The “limitation” is not very noticeable.

Question 19

Green Bank Telescope

Answer 19

Land
Radio/Microwave

Question 20

VLA Telescope

Answer 20

Land
Radio/Microwave

Question 21

Spitzer

Answer 21

Space
Infrared

Question 22

Kepler

Answer 22

Space
Visible

Question 23

Arecibo Telescope

Answer 23

Land
Radio/Microwave

Question 24

Gemini

Answer 24

Land
Visible

Question 25

TESS

Answer 25

Space
Visible

Question 26

Herschel

Answer 26

Space
Infrared

Question 27

SOPHIA

Answer 27

Plane
Infrared

Question 28

KECK

Answer 28

Land
Visible

Question 29

Hubble

Answer 29

Space
Visible

Question 30

CARMA

Answer 30

Land
Radio/Microwave

Question 31

Chandra

Answer 31

Space
X-ray

Question 32

FERMI

Answer 32

Space
Gamma Ray

Question 33

HESS

Answer 33

Land
Gamma Ray

Question 34

Swift

Answer 34

Space
Gamma Ray

Question 35

Planck

Answer 35

Space
Radio/Microwave