Lecture 4 — Techniques of Astronomy (white background) -...

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PHYS 1160Introductory Astronomyand the Search for LifeElsewhereLecture 4Techniques ofAstronomyThis Lecture• TelescopesInstruments for optical astronomyRadio AstronomyObservations from Space2
TelescopesTelescopes have been the keytool for astronomical researchsince their use by Galileo in1609.Galileo’s telescopes and manyother early telescopes wererefractingtelescopes.Today most telescopes forprofessional astronomy arereflectingtelescopes.34Refracting telescopeA refracting telescopecollects light with atransparent lens.The picture shows the 1mrefractor at the Yerkesobservatory in Chicago.1 metre is about the largestfeasible size for a lens sothis design cannot be usedfor very large telescopes.The lens becomes so heavy itwill deform under its ownweight.
5Reflecting TelescopesReflecting telescopes usea curved mirror instead ofa lens to focus light.The picture shows the 8mGemini North Telescopeat Mauna Kea, Hawaii.This type of design isused for most modernastronomical telescopes.6Key features of a TelescopeLight collecting power– This is determined by theapertureof thetelescope - i.e. the diameter of its mirror orlens.– A bigger telescope collects more light and cantherefore see fainter stars or galaxies.Resolving Power– Or angular resolution is the telescope’s abilityto see fine detail.– This also depends on the telescope’s aperture.For these reasons bigger is always betterwhen it comes to telescopes.
7Mount Wilson100-inchThe 100 inch (2.5m) telescopeThe 100 inch (2.5m) telescopeat Mount Wilson observatoryat Mount Wilson observatory(near Los Angeles) was(near Los Angeles) wascompleted in 1917.completed in 1917.It made important discoveriesIt made important discoveriesincluding Edwin Hubbleincluding Edwin Hubble’swork on the distances ofwork on the distances ofgalaxies.galaxies.85m Hale Telescope, Mount Palomar (1948)5m Hale Telescope, Mount Palomar (1948)
910m Keck Telescopes, Mauna Kea Hawaii10m Keck Telescopes, Mauna Kea Hawaii10Segmented Mirror of the Keck TelescopeSegmented Mirror of the Keck Telescope
Extremely Large Telescopes11Even larger telescopes – known as Extremely Largetelescopes (or ELTs) are now being designed.ThirtyThirtyMetreMetreTelescope (TMT)Telescope (TMT)ObservingHow are telescopesused?

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Term
Three
Professor
Bailey
Tags
Astronomy, Telescopes, Hubble Space Telescope, radio telescopes, Keck Telescope, Very Large Telescope

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