lec15 - Lecture 15 Astronomical Observations Lecture 15...

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Unformatted text preview: Lecture 15 Astronomical Observations Lecture 15 Purdue University, Astronomy 364 1 Reminder Exam #1 at 8-9 pm on Monday (see details on course web page). There will be no class on Monday. Lecture 11 Purdue University, Astronomy 364 2 Detectors Photoemissive detectors Emission of electrons upon absorption of photons, i.e., photoelectric effect e.g., photomultiplier tube or PMT Photoconductive detectors Accumulation of electric charges locally upon absorption of photons e.g., charge coupled device or CCD Quantum efficiency The probability of an incident photon producing a photoelectron or an electron-hole pair Lecture 15 Purdue University, Astronomy 364 3 Photon Counting Lecture 15 Purdue University, Astronomy 364 4 The number of photons detected ( x ) follows Poisson distribution: P ( x , ) = x x ! e , x = , 2 = If the observation is photon limited , i.e., the noise is dominated by statistical fluctuation, the signal-to-noise ratio is S N = 1/2 If the observation is background limited , the signal-to- noise ratio is S N s b = s b 1/2 General Case Lecture 15 Purdue University, Astronomy 364...
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This note was uploaded on 04/23/2011 for the course ASTR 364 taught by Professor Cui,weik. during the Spring '11 term at Purdue University-West Lafayette.

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lec15 - Lecture 15 Astronomical Observations Lecture 15...

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