Unit 3 (Telescopes): "Telescopes & Spectroscopy" Flashcards
Why is building Telescopes on Mountains beneficial?
There’s less air to see through.
What is an aperture and what does it do?
A hole in the lens that controls how much light gets into the telescope
Chromatic Aberration is primarily a problem for which type of telescope?
Refracting Telescopes
What is Chromatic Aberration?
A color distortion = an outline of unwanted color along an object edge
How can you reduce Chromatic Aberration?
Using an achromatic lens; puts focal points in the same location) OR use a longer tube.
What types of telescopes are ground-based? What types are space-based?
Ground-based = reflecting &
Space-based = refracting
What is the difference between an emission spectrum and an absorption spectrum?
An emission spectrum = colored lines;
Absorption spectrum = dark-colored lines
What are some uses of spectroscopy?
Determines how each type of molecule/ atom will reflect, absorb, or emit electromagnetic radiation.
Reflecting Telescope Pros
- 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)
Do all elements have the same emission spectrum?
No; different numbers of protons & arrangements of electrons.
Reflecting Telescope Cons
- Periodic mirror cleaning
- Mirror must be realigned after cleaning (expensive)
- Improper alignment = blurry images
- Periodic mirror polishing (tarnished due to air exposure)
What is spectroscopy?
- 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)
Refracting Telescope Pros
- 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)
True or False: All elements have unique, distinct spectral lines.
True
What does diffraction grating do?
An optical element that divides light composed of different wavelengths into light components by wavelength
Refracting Telescope Cons
- 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)
Hybrid Telescope Pros
- “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.
Hybrid Telescope Cons
- 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.
Green Bank Telescope
Land
Radio/Microwave
VLA Telescope
Land
Radio/Microwave
Spitzer
Space
Infrared
Kepler
Space
Visible
Arecibo Telescope
Land
Radio/Microwave
Gemini
Land
Visible
TESS
Space
Visible
Herschel
Space
Infrared
SOPHIA
Plane
Infrared
KECK
Land
Visible
Hubble
Space
Visible
CARMA
Land
Radio/Microwave
Chandra
Space
X-ray
FERMI
Space
Gamma Ray
HESS
Land
Gamma Ray
Swift
Space
Gamma Ray
Planck
Space
Radio/Microwave
