Telescope-Objective-and-Eyepiece望远镜的物镜与目镜课件

1、Observatories and TelescopesMauna Kea, Hawaii (14,000 ft)Why do telescopes need to be located at high altitude and dry climate ?Observatories and TelescopesMTelescopes Mirrors and Lenses Telescopes are basically a large mirror (reflecting) or a lens (refracting) Consider the human eye as telescope W

2、hat determines the “power” of a telescope ?Telescopes Mirrors and LenseCollecting AreaLensRetinaEye could be a “refracting” telescope,but the size is very smallCollecting AreaLensRetinaEye cCollecting Area = Power A = p ( d / 2)2 ; d diameter Diameter of the telescope indicates its power Largest opt

3、ical telescope: Keck 1 and 2, each with a mirror of 10 m diameter Large Binocular Telescope (LBT): Ohio State, Arizona, Germany, Italy Two 8.4 m mirrors in a binocular shaped mount HST Only 2.4 m, but with a huge advantage How much more powerful than HST is the Keck (neglecting that advantage) ? New

4、 30m telescope on the drawing boardCollecting Area = Power A = p Large Binocular TelescopeMount Graham, ArizonaLarge Binocular TelescopeMounTelescope-Objective-and-Eyepiece望远镜的物镜与目镜课件Objective and eyepieceObjective and eyepieceTelescope Objective and Eyepiece The main function of a telescope is to c

5、ollect as much light as possible from the source, NOT to magnify an image Need bigger and bigger telescopes! The main mirror or lens of a telescope is called the OBJECTIVE The Eye-Piece (small lens or mirror) is to magnify the image after it is formed from the light collected by the objectiveTelesco

6、pe Objective and EyepProperties of Light and Telescopes Reflection Mirrors Refraction LensesProperties of Light and TelescSimple Refracting TelescopeObjective LensSecondary Lens (Eyepiece)FocusConvex lensSimple Refracting TelescopeObjSpheres of light from distant source parallel rays at the observer

7、Spheres of light from distant Different speeds in different media Bending or RefractionDifferent speeds in different Refraction of light beamLight bends towards the perpendicular going into denser medium, and vice-versa Normal(Perpendicular)Refraction of light beamLight Refraction by prism and lensR

8、efraction by prism and lensRefractive Index Speed of light slows down in a medium ! The ratio of the speed of light in vacuum to the speed in a medium c / v = m mu is called the Refractive Index Material R.I. Water 1.33 Glass 2.6 Bending of light (diffraction) depends on R.I of the medium and wavele

9、ngth of light lRefractive Index Speed of lighChromatic Aberration:Different colors at different focusChromatic aberration affects refracting telescopes; therefore use reflecting telescopes in modern observatoriesChromatic Aberration:DifferenLaw of Reflection: Angle i = Angle rLaw of Reflection: Angl

10、e i = APrimaryMirrorPrime FocusSecondary MirrorCassegrain FocusREFLECTING TELESCOPESPrimaryPrime Secondary CassegrReflecting Concave MirrorReflecting Concave MirrorTelescopic ConfigurationsTelescopic ConfigurationsSpherical and Parabolic Mirrors Spherical and Parabolic MirrorWavelength range of obse

11、rvatories and telescopes Ground based telescopes can measure - Visible (4000-7000 A), - Near-IR (0.7-2 microns), 1 mm = 10000 A - Radio ( 1 mm or greater) All other wavelengths blocked out by the atmosphere Space based observatories for Gamma ray, X-ray, UV, and Far-IR astronomyWavelength range of o

12、bservatorVisible (Optical) and Radio “Windows” in the AtmosphereVisible (Optical) and Radio “WRadar and Radio Astronomy Radio telescopes (like huge satellite dish) collect radio waves from astronomical objects Radar telescope = Transmitter + Radio Telescope Doppler Radar Transmits radio waves toward

13、s an object and collects reflected radio waves; spread in signal shows distance and velocity Largest radio telescope is the Arecibo, 1000 ft diameter, in Puerto Rico Radar and Radio Astronomy RadiRadio TelescopeRadio TelescopeAracebo Radio Telescope(Puerto Rico)Aracebo Radio Telescope(PuertoRotation

14、al Speed and Doppler Shift(Line profile broadens on both the blue and red side)Doppler RadarRotational Speed and Doppler SHubble Space TelescopeHubble Space TelescopeGround and HST imagesUnresolved ResolvedGround and HST imagesUnresolveVisible and IR images of SaturnVisible and IR images of SaturGamma-Ray View of the SkyEach wavelength band presents a different and mutually complementary viewGamma-Ray View of the SkyEach Telescope and InstrumentsTelescope and InstrumentsIntensities of Lines in Absorption Spectra: Atoms ab