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Lecture4ASTJan26_1

# Lecture4ASTJan26_1 - AST1002 Lecture 4 Schedule For Today...

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1 Schedule For Today: Follow up on Fusion. Reading assignment on Mercury Posted. AST1002 Lecture 4 http://www.iter.org/ Brian Greene discussing multiple universes posted. Recap Ch. 2 Ch. 3 Telescopes Main Points: Types of telescopes Astronomer’s tricks of the trade. Telescopic horse power Light gathering power Resolution Telescopes at different wavelengths How to focus, and what do they see? Ch. 3 Telescopes Different telescopes for different wavelengths Hubble: visible + IR ubble Hubble Space Telescope (HST) X-ray Optical Crab Nebula: Remnants of Radio IR supernova 1054 seen by the Chinese. Seen near the constellation aurus Taurus. Light goes more slowly in a medium: v = c/n n is the index of refraction: depends on e wavelength of light θ 1 θ 2 ( violet) θ 2 ( red) the wavelength of light and the medium Chromatic Aberration Snell’s Law: Sin( θ 1 )/Sin( θ 2 ) = n 2 /n 1 θ 1 θ 2 n 1 n 2 Here n 1 <n 2

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2 o f i Optical Telescopes: Violet (400 nm to Red 700 nm): In the “100’s of nanometers range” From high school…. 1/f = 1/o +1/i o is at infinity then f = i o f i Focal length = f , constant Image distance = i Object distance = o If o is at infinity, then f i We can think of star light as coming in from infinity. Refractive and Reflective: Glass lens or mirror Fundamental Idea: Collect a large area of light from an object, and focus it down to an image on a focal plane, and then look at the image with a magnifying glass. Magnification: F o /F e Yerkes – 1 m refractor (Still the largest single rimary lens primary lens system.) But mirrors are better, since the light does not have to pass through the main lens. Newtonian Telescope: Focusing mirror, flat mirror at 45 o , eyepiece Cassegrain Telescope: Focusing mirror, secondary mirror on optical axis, eyepiece
3 Hubble’s 2.4 m reflector mirror Primary focus Parabolic mirror! Schmidt-Camera

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Lecture4ASTJan26_1 - AST1002 Lecture 4 Schedule For Today...

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