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Telescope
• An instrument that collects electromagnetic radiation from objects in space
• Concentrates the electromagnetic radiation for better observation
Optical Telescopes
Most common type of telescope
Used to study visible light from objects in universe
Enables you to see millions of stars
Two Disadvantages of Refracting Telescopes
1. Images cannot be perfectly focused
2. Size of objective lens limits the size of the telescope
Three Advantages of Reflecting Telescopes
1. Large mirrors can gather more light.
2. Flaws in the mirror’s glass do not affect the light.
3. Mirrors can focus all colors of light at the same time.
Optical Telescopes & Atmosphere
Air above telescope makes starlight shimmer & blur.
Light pollution affects ability to see dim objects.
Placement of Telescopes
Dry environments
Mountaintops Less light pollution Less air pollution Air is thinner
Space
Detecting Electromagnetic Radiation
EM spectrum = all of the wavelengths of
electromagnetic radiation
Each color of light is a different wave-
length.
Humans can see radiation from red light
(long wave) to blue light (shorter wave).
Nonoptical Telescopes Used to study
invisible radiation
Each type of EM radiation gives different clues about objects
Detecting Electromagnetic Radiation Visible light is small part of EM
spectrum.
Most of EM spectrum is invisible Radio waves (longest waves) Microwaves Infrared waves Ultraviolet waves X-rays Gamma waves (shortest waves)
Radio Telescopes
Detect radio waves
Can be linked with other radio telescopes
Surface does not have to be solid
Must be much larger than optical telescopes Radio waves can be as large as a
building