Transcript Telescopes
Telescopes Telescope History Galileo Galilei built first refractive telescope in 1609 Isaac Newton built the first reflective telescope in 1668 1st Reflecting Telescope by Isaac Newton Optical Telescopes Telescopes that contain mirrors, lenses, or both Three properties: • Light-gathering power • Resolving power • Magnifying power Optical Telescopes Telescopes with larger mirrors/lenses: • Can“see”farther into space • Have greater resolution Magnification can be changed by using different eyepieces Usually placed on mountain tops to reduce city lights Refracting Telescopes Telescope uses two lens to bend or refract light Simplest of all telescopes First refracting telescope capable of magnifying objects 30 times. Objective Lens Most important lens is the objective lens • Bends the light from a distant object and focuses the light at the focus to produce an image • The objective lens produces a very small, bright image of an object Focus= central point Focal length= distance between the focus and the objective lens Eyepiece Lens The second lens used in a refractive telescope Eyepiece magnifies image produced by the objective lens Simple Refracting Telescope Disadvantages Shorter wavelengths of light are bent more than the longer ones Chromatic aberration: • Weakens image and creates a halo of color around it • When red light is in focus, a bluish halo appears. Very hard to produce a large piece of high-quality, bubble-free glass Yerkes Observatory Largest Refracting Telescope Yerkes Observatory Williams Bay, Wisconsin Refracting Telescope at Lick Observatory Southern California Lick Observatory Reflecting Telescopes Uses a concave (curved) mirror that focuses the light in front of it Mirror is coated in a highly reflective material, an aluminum compound Two mirrors- one large & concave and one small & flat Reflecting Telescope Advantages No Chromatic aberration because reflected light is not dispersed into its component colors. Glass does not need to be highquality because light does not pass through it. Disadvantage–secondary mirror blocks some light entering the telescope. Mount Palomar Observatory California Mirror for Hale Telescope at Mount Palomar Observatory Hale Telescope Keck Telescopes World’s Largest Reflecting Telescopes Hawaii Schematic of Keck Multiple Mirros Telescope (MMT) Kitt Peak Observatory Arizona La Palma Observatory Canary Islands, Spain McDonald Observatory Texas Cerro Tololo Observatory Chile Invisible Light Stars produce light wavelengths that are not visible to our eyes • Gamma rays, X-rays, ultraviolet radiation, infrared radiation, and radio waves • Most of these can not get past our atmosphere… so we must get our cameras above it! Radio Telescopes These big dishes are used to detect radio waves Focuses incoming radio waves on an antenna and transmits these to an amplifier. Radio Signals Radio signals are weak so it requires a very large dish These telescopes have poor resolution • Radio Interferometer= Wire several telescopes together Advantages Less affected by turbulence in the atmosphere, clouds, and weather No protective dome is required = cheaper Can be used and “viewed” 24 hours a day Radio signals can pass through intersteller dust clouds Disadvantages Can be affected by human-made radio interference • Usually placed in valleys to block interference Largest Radio Telescope in World Arecibo, Puerto Rico VLA Radio Telescope Socorro, New Mexico VLA Space Telescopes Orbit above Earth’s atmosphere and produce clearer images Hubble Space Telescope Built by NASA and sent in April 1990 10 billion times more light-gathering power than the human eye Given us amazing images of space www.hubblesite.org Other Space Telescopes Chandra X-Ray Observatory • NASA uses to study X-rays • Launched in 1999 • Gather data about black holes Compton Gamma-Ray Observatory • Used to study visible light and gamma rays In 2018, NASA will launch James Webb Space Telescope to study infrared radiation • Run into many obstacles and budget problems