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Section 1-2
Telescope: Gathers
electromagnetic radiation
from objects in space
Optical Telescopes
• Most common
• Studies light
• There are millions, but only 3000 without a
telescope
• Focuses light to a focal point; where rays of light
pass through
Optical telescopes continued
• Objective lens: collects light and forms an
image at the back of the telescope
• Eyepiece: Magnifies the image
Refracting telescope
• Uses glass lenses to gather and focus light
• Disadvantages:
– Cannot focus perfectly
– Size is limited by the size of the objective lens
(Large lenses distort the image)
Reflecting telescope
• Uses a curved mirror to gather and focus light
• Large mirror reflects light to a flat mirror
• Advantages:
– Large mirrors allow more light to be gathered
– Mirrors are polished, so flaws don’t affect the light
– Mirrors can focus all colors of light at the same
focal point
Very Large Telescopes
• Use several mirrors which allows more light to
be gathered in the same area
• Keck Telescopes in Hawaii use 36 hexagonal
mirrors
Optical telescopes in space
• This will avoid interference by the atmosphere
(layer of gases surrounding the Earth)
• Hubble Space Telescope is 2.4 meters across,
but can detect very faint objects in space
The Electromagnetic Spectrum
• Made up of wavelengths of electromagnetic
radiation (light)
• James Maxwell proved that visible light is part
of the EMS in 1852
• Detecting Electromagnetic Radiation
– Humans can only see visible light
Non-optical telescopes
• To study invisible light scientists must use nonoptical telescopes
• Detects different types of radiation
Radio telescopes
• Detects radio waves
• Since very little radio radiation reaches the
Earth, they must be very sensitive
• When linked together, they work like a single
telescope
Non-optical telescopes in space
• Most Electromagnetic waves are blocked by
the Earth’s atmosphere, scientists put them in
space
• Chandra X-ray Observatory is a space
telescope that detects x-rays
• Other types include:
– UV telescopes, infrared telescopes, and gamma
ray telescopes