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Telescopes
• Collect more light than eye
• More detailed images than human eye
• Larger aperture is better– Aperture refers to the diameter of the primary
lens or mirror of telescope
• Magnification is useless without:sensitivity and resolution are crucial
Refractor Telescope
Reflector Telescope
Reflectors
Sensitivity
Compound Mirror:
Diffraction Pattern
Angular Resolution
• Larger aperture (diameter) telescopes have smaller diffraction patterns
• The smaller the diffraction patterns result in better angular resolution (more detail)
• Diffraction limit in arcseconds = 2.5 105 (/D) = wavelength D = aperture
• Smallest detail that can be resolved
Bigger is Better
1. Better sensitivity: more light gathering area
2. Better angular resolution in most instances: more detail
Figure shows effect of larger aperture
Seeing: Atmospheric Effect
Why Put a Telescope in Orbit?
• The only reason to put a visible light telescope in space is to improve resolution!
• a) ground-based b) damaged Hubblec) enhanced image d) repaired Hubble
Atmospheric Windows
• Certain wavelengths require orbiting telescopes• Radio and visible light can be done from ground
Mauna Kea