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This 25 page Class Notes was uploaded by Mrs. Linda Wiegand on Friday September 18, 2015. The Class Notes belongs to PHY 2054 at University of Florida taught by Staff in Fall. Since its upload, it has received 24 views. For similar materials see /class/206766/phy-2054-university-of-florida in Physics 2 at University of Florida.
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Date Created: 09/18/15
26 PHY2054 Chapter 25 Telescopes Main purposes 9 Resolution of closely spaced objects oLight collection measure spectra see distant and dim objects Resoution through magnification 0mg 2 fobjective feyepiece discussed in textbook Light collection compare to eye oPupil of eye D m 8mm in very dim light oLargest telescope Keck has D 10m oRatio of areas IO00082 15 x 106 oCan collect light for hours rather than 01 sec 9 More sensitive light collectors CCD arrays Large telescopes favored by several bYI39on over eye oCan see near the end of the known universe PHY2054 Chapter 25 27 Stellar Spectra telescope diffraction grating llllll Spectrum of star Helium PHY2054 Chapter 25 28 Main Limitation on Earth Atmosphere Air cells in atmosphere oAir cells above telescope mirror cause distortion of light oBest performance is z 025 05 resolution on the ground oThis is why telescopes are sited on high mountains Adaptive opticsquot just beginning to offset this distortion Two main components in adaptive optics oMechanism to measure wave distortion above mirror oActuators under mirror move surface to offset distortions o Easier for infrared wavelengths than for optical wavelengths PHY2054 Chapter 25 29 Adaptive thics Gemini Teieswpe Gemini twins gt D 8 i m gt Hawaii Chile gt 0th outfitiiedi with adaptive optics Adaptive Optics in Infrared 936 nm Imaging with Hukupz 1 9x better PHYZEISA chapmzs Gemini North Images 7x Improvement PHYZEISA ChapterZS Theoretical Performance Limit Diffraction Light rays hitting mirror spread due to diffraction oThese rays interfere just like for single slit oCalculation a little different because of circular shape oAngle of spread A6 122MD D diameter Intensity vs angle 1 08 06 04 122 ND 122 MD 02 I 2 1 0 1 e in units of MD PHY2054 Chapter 25 33 Example Optical Telescopes Keck telescope D 10m 7 550nm 9A6 122 x 550 x 109 10 67 x 10398 rad 0014 oCompare this to 025quot 05quot from atmosphere Hubble space telescope D 24m A 550nm 9A6 122 x 550 x 10399 24 28 x 10397 rad 0058quot 9 But actually can achieve this resolution Rayleigh criterion oTwo objects separated by A6 lt 122MD cannot be distinguished oAn approximate rule shows roughly what is possible PHY2054 Chapter 25 34 n Mum and ITS Mlt n Charm m m N rth w g3t QCLDESBEBW rcaw mtim magca Hwbb g amech PHY2054 Chapter 25 35 P um Seen by Keck w Adaptive th cs Kem wt mn 2 035 2 2 Lu gm 2MB PHY2054 Chapter 25 36 New Mum Mommas Seen with Adaptive Optics Chmn NIX and Hydra em wtwm 2 6335 A 2 16me 2m Star trails PHY2054 Chapter 25 37 Single Star one point One point 0 theta Units in multiples of MD PHYZOSA Chapter 25 38 Two Stars Separation 20 MD Twn points separatinn 20 Two points separation 20 1 0 1 theta Units in multiples of MD PHY2054 Chapter 25 39 Two Stars Separation 15 MD Two points separation 150 Two points separation 15 0 theta Units in multiples of MD PHY2054 Chapter 25 40 Two Stars Separation 122 MD Two points separation 122 Two points separation 122 0 theta Units in multiples of MD PHY2054 Chapta39 25 41 Two Stars Separation 10 MD Two points separation 10 1 6 1 theta Units in multiples of MD Two points separation 100 PHYZOSA Chapter 25 Two Stars Separation 08 kD TWquot Paintsy separation 08 Two points separation 080 0 theta Units in multiples of MD PHYZOSA ChayterZS 43 Two Stars Separation 06 kD TWO Pailltsy separatiml 06 Two points separation 060 U w 0 theta Units in multiples of MD PHYZOSA Chapta 25 44 Two Stars Separation 04 kD Two pointsY separation 04 Two points separation 040 16 14 12 0398 I 06 04 02 U x w 0 theta Units in multiples of MD PHYZOSA ChayterZS 45 Single Star One point One polnt 1 08 06 I 04 02 gt U x w 2 0 A theta Units in multiples of AD FHYZUSA Chapter 25 46 Interferometry Multiple Radiotelescopes Combine information from multiple radiotelescopes oAtomic clocks to keep time information time phase 9 Each telescope records signals on tape with time stamp oTapes brought to correlator to build synthetic image Single telescope resolution 0A0 122MD D diameter of dish or mirror Two telescope resolution 9A0 MD D distance between telescopes Spectacular improvement in resolution 9 Diameter of dish 20 50m oDistance between two dishes 12000 km diameter of earth oImprovement is factor of 200000 500000 PHY2054 Chapter 25 47 Radiotelescope at MaLLna Kea Hawaii Interferometry using widelyspaced radiotelescopes Quasar I Hydrogen maser clock accuracy 1 sec in 1 million years n r 7 39 Acquisition 7 Data 1 I Acquisition
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