Introduction130

6.2 Position-insensitive detectors 131 Photomultiplier and photometry • Proportional counter

6.3 Position-sensitive detectors 137 Position-sensitive proportional counters • Charge-coupled device - Structure of a CCD - Exposure to light - Readout of the image - Utility in optical astronomy - Adaptive imaging -Utility in x-ray astronomy

6.4 Gamma-ray instruments 145 EGRET experiment • Detector subsystems - Plastic scintillator anticoincidence - Spark chamber detection of electron-positron pair - Timing scintillation detectors (up-down discrimination) - Energies and arrival directions • BATSE experiment

6.5 Statistics of measurements 151 Instrumental noise • Statistical fluctuations - "noise" -

Poisson distribution - Normal distribution - Variance and standard deviation - Measurement significance -Statistical traps • Background - Propagation of errors - Background subtraction - Low and high background limits - Bright and faint source observations • Comparison to theory - Finding parameters and checking hypotheses - Least squares fit - Chi square test

7 Multiple telescope interferometry 175

7.1 Introduction 176

7.2 Two-telescope interference 177

Principle of interferometry • Equatorial observation -

Transmission of radiation - Reception - Earth rotation -Position of source • North-Pole observation • All-sky fringe patterns • Point-source response - Wavefront samples -

Summed waves - Multiplied waves - Signal processing • Fourier plane - Spatial frequencies - Projected baseline

7.3 Mapping the sky Cross-correlation or "shading" method - Bins on the sky -

Cross-correlation - Equal weighting of time intervals • Fourier analysis of sky brightness - Principle of aperture synthesis - Arbitrary sky brightness distribution - Visibility -Phase of visibility function - Sky brightness • Cleaning algorithms

7.4 Arrays of telescopes Multiple baselines • Radio arrays • Very long baseline interferometry (VLBI) • Optical and x-ray interferometry

Telescopes Mastery

Telescopes Mastery

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