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

Vienna

Lick

YerkesObservatory

20th century Large Reflectors Come of Age

Mount Wilson

Palomar (5-m)

4 meter Reflectingtelescope

Objective Mirror

Dome of 4 meterKitt 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 onthis side

Good seeingon this side

Electromagnetic Spectrum

Radio TelescopesArecibo

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