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 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 sky at 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