anthony morris
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Telescope

  • Bigger is better
    • Bad for glass refractors
      • Hard to make
      • Weight causes sagging
      • Air bubbles distort
      • Opaque at some wavelengths
    • Largest visible-light telescopes today have 8 to 10 meter mirrors
  • On ground
    • Stable, controlled
    • Bigger dishes
    • Atmospheric blurring
  • In space
    • No atmosphere
    • Expensive
    • Difficult to maintain

Refactor Telescopes

  • Uses a lens to gather and focus light
  • First telescopes built
  • Advantages
    • Rugged
    • Rarely needs cleaning (glass is sealed inside)
    • Tube is closed off from outside air so air/temperature has less impact
  • Disadvantages
    • Chromatic aberration
      • Colour deviation or distortion

Reflecting Telescopes

Types of reflecting telescopes

  • Usually have two mirrors
    • Primary
    • Secondary
  • Configurations
    • Newtonian
    • Cassegrain
    • Nasmyth/Coudé
      • Commonly used as professional telescopes
  • Advantages
    • No chromatic aberration
      • All wavelengths of light reflect off the mirror the same
    • Easily made to be big
    • Cheaper than refractors of the same size
    • Only one side of the objective needs to be perfect (reflecting vs. passing through)
  • Disadvantages
    • Easy to get optics out of alignment
    • Optics need frequent cleaning
    • Two mirrors --> can produce diffraction effects
      • "Christmas star" effect

Radio Telescopes

  • Radio waves
  • Observe at any time of the day
  • Wire meshes or dishes
    • Parabolic shape focuses the light to a single point
  • Large because radio wavelengths are much longer than optical wavelengths

Infrared/Ultraviolet Telescopes

  • Infrared or ultraviolet rays
  • Very similar to optical telescopes in design
  • Very little radiation of these types make it to the ground

Astronomy