Telescopes

Telescopes

• Act as “electromagnetic radiation catchers”• Capture as much as possible

• Focus

• Magnifies images

Telescopes that “catch” visible light are called optical telescopes.

Telescope Terms

• magnification (power) – how strong the telescope is.

• resolution - how close two objects can be and yet still be detected as separate objects.

• aperture – diameter of the lens or mirror

Reflector Telescopes

• Isaac Newton developed the reflector about 1680.

• Newton used a curved, metal mirror to collect the light and reflect it to a focus.

• Because the mirror reflected light back into the tube, he had to use a small, flat mirror in the focal path of the first mirror to deflect the image out through the side of the tube, to the eyepiece; otherwise, his head would get in the way of incoming light.

                                             

Reflector Telescope Diagram

Refractor Telescopes• Galileo (1609) is the first to use it for astronomy.

• The objective lens gathers the light, and bends or refracts it to a focus near the back of the tube. The eyepiece lens brings the image to your eye, and magnifies the image.

• Refractors have good resolution, high enough to see details in planets and stars.

• It is difficult to make large objective lenses (greater than 4 inches or 10 centimeters) for refractors.

• Refractors are relatively expensive

                                     

Refractor Telescope Diagram

                               

                       

Refractor vs. Reflector

                                           

Compound Telescopes• The first compound telescope was made by

German astronomer Bernhard Schmidt in 1930

• The compound telescope is the best, all-around telescope, good for viewing lunar and planetary observations. It is portable and compact and is the most versatile

• Uses a combination of mirrors to fold light rays and form an image.

• Has an equatorial mount that allows it to spin in every direction.

Compound Telescope Diagram

Multiple Mirror Telescopes (MMT)

• Works like a reflecting telescope, but uses many mirrors to create 1 large mirror.

• Can create bigger mirrors

• Mirrors weigh less and distort less

                                              

Hubble Telescope

• Hubble orbits 600 kilometers (375 miles) above Earth, working around the clock to unlock the secrets of the Universe. It uses excellent pointing precision, powerful optics, and state-of-the-art instruments to provide stunning views of the Universe that cannot be made using ground-based telescopes or other satellites.

Hubble Images

The Very Large Telescope (VLT)

• Cerro Paranal, Chile

• Uses 4 separate large telescopes as well as several other small telescopes to create 1 large telescope.

• The large telescope mirrors are 8 meters across.

Electromagnetic Spectrum

Radio Telescopes

• Karl Jansky inadvertently discovered galactic emissions of radio waves in 1933

• Like optical telescopes, radio telescopes have reflectors and receivers

• Most radio telescopes need to be large in order to accommodate radio's longer wavelengths and lower energies

• Can “see” day or night

Arecibo (Puerto Rico)

The main reflector is 1000 feet in diameter

It can see 1/3 of the skyat a time

The Very Large Array (VLA)New Mexico

The VLA is equivalent to a dish 22 miles across

Other Eyes

• X-Ray

• Infrared

• Gamma Ray

The Milky Way Galaxy

• Radio

• Infrared

• Visual

• X-Ray

• Gamma Ray

The End