Transcript Telescopes
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 o 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-ofthe-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