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Astro-Tools of the Trade

Astro-Tools of the Trade - o Uses a mirror to bring light...

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Tools of the Trade Primary purpose is to collect more light Typical large telescope: D = 6 m mirror o Dilated pupil: d = 6mm A = area = piR^2 = pi D^2/4 Ratio of areas =A 2 /A 1 = D 2 2 /D 2 1 = (D 2 /D 1 ) 2 A large telescope also provides higher resolution – the ability to detect fine detail. o But turbulence in the atmosphere blurs the image (at optical wavelengths especially) o Atmosphere throws the light around from the stars With a long exposure you’d just get one big blur Refracting Telescopes o Light is bent (“refracted”) by lens and brought to a focus o Binocular = a pair of small refracting telescopes o Purpose of a telescope is to take a large area of light and concentrate it into a small area o Galileo first to use telescope for astronomy o James Lick – donated his fortune to build an observatory in San Jose o Simple to make, but they suffer from several problems, including chromatic aberration Different colors of light focus at different lengths Reflecting Telescopes
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Unformatted text preview: o Uses a mirror to bring light to a focus o Suffer from spherical aberration – if curve is not the right angle o Paraboloid or hyperboloid allow for a single focus • Radio Telescope o Much bigger areas needed • Telescopes in Space o Advantages: No distortion by atmosphere Darker sky (especially for infrared) You can’t get all of the different kinds of light from the ground • Uv/x-ray/gamma ray/infrared/ O-Zone, water vapor, and other molecules are bypassed • Twinkiling of Stars o Air bends starlight Due to atmospheric turbulence, the bending varies with time, so the amount of light hitting your eye varies. o Star closer to horizon – more air, more turbulence – more twinkling. o This is related to blurring of a star’s image: it doesn’t like point-like. o Planets don’t usually twinkle, stars do • Adaptive Optics o Changes the light waves to flat when they are actually jumping around...
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