Telescopes
Galileo 1609
The Moon as a World
Jupiter has Moons
Refracting telescopes
Isaac Newton’s reflecting telescope
Reflecting telescope
Objective mirrors instead of lenses
Three Powers
• Magnifying
• Resolving
• Light Gathering
Magnifying Power
• Ability to make objects appear larger in
angular size
• One can change the magnifying power of
a telescope by changing the eyepiece
used with it
• Mag Power = focal length of objective
divided by the focal length of the eyepiece
Resolving Power
• Ability to see fine detail
• Depends on the diameter of the objective
lens or mirror
Light Gathering Power
• The ability to make faint objects look
brighter
• Depends on the area of the objective lens
or mirror
• Thus a telescope with an objective lens 2
inches in diameter has 4 times the light
gathering power of a telescope with a lens
1 inch in diameter
Herschel & Lord Rosse
19th century: epoch of the large
refractors
Refracting telescopes
Lick
Vienna
Yerkes
Observatory
20th century Large Reflectors Come
of Age
Mount Wilson
Palomar (5-m)
4 meter
Reflecting
telescope
Objective Mirror
Dome of 4 meter
Kitt Peak
Keck Telescopes
Rooftop telescopes
MSU Campus Observatory
SOAR Telescope
SOAR Telescope -- Cerro Pachon
Astronomical “seeing”
• Blurring effect of looking through air
• Causes stars to twinkle
Bad seeing on
this side
Good seeing
on this side
Electromagnetic Spectrum
Radio Telescopes
Arecibo
Very Large Array
Very Large Array
Observing from space
• No clouds
• Perfect seeing
• Can see wavelengths of light blocked by
the earth’s atmosphere
Hubble Space Telescope