Book contents
- Frontmatter
- Contents
- List of figures
- List of tables
- Preface
- Acknowledgments
- 1 Astronomy through the centuries
- 2 Electromagnetic radiation
- 3 Coordinate systems and charts
- 4 Gravity, celestial motions, and time
- 5 Telescopes
- 6 Detectors and statistics
- 7 Multiple telescope interferometry
- 8 Point-like and extended sources
- 9 Properties and distances of celestial objects
- 10 Absorption and scattering of photons
- 11 Spectra of electromagnetic radiation
- 12 Astronomy beyond photons
- Credits, further reading, and references
- Appendix: Units, symbols, and values
- Index
6 - Detectors and statistics
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- List of figures
- List of tables
- Preface
- Acknowledgments
- 1 Astronomy through the centuries
- 2 Electromagnetic radiation
- 3 Coordinate systems and charts
- 4 Gravity, celestial motions, and time
- 5 Telescopes
- 6 Detectors and statistics
- 7 Multiple telescope interferometry
- 8 Point-like and extended sources
- 9 Properties and distances of celestial objects
- 10 Absorption and scattering of photons
- 11 Spectra of electromagnetic radiation
- 12 Astronomy beyond photons
- Credits, further reading, and references
- Appendix: Units, symbols, and values
- Index
Summary
What we learn in this chapter
The detectors at the foci of telescopes may be position-insensitive such as the classic photomultiplier and the simple proportional counter. Position-sensitive detectors at the focus of a telescope provide an overall field of view that includes many beams (resolution elements). The charge-coupled device is widely used in optical and x-ray astronomy for this purpose. Its internal structure and operation reveal its strengths and weaknesses. Gamma-ray astronomers use plastic and crystal scintillators and spark chambers or their equivalent. Examples are the EGRET and BATSE instruments that were in orbit during the 1990s. The precision of a detected signal is limited by statistical and systematic errors. Knowledge of basic statistical theory enables one to assess the significance and meaning of one's data. Aspects of this are the character of statistical fluctuations (the Poisson and normal distributions), background subtraction with error propagation, and comparison of data to a model with a least squares fit and the chi square test.
Introduction
At the focal plane of a telescope, an image is formed. It can be viewed directly by eye in two ways, on a piece of frosted glass placed in the focal plane or through an eyepiece. In the latter case, the focal point of the eyepiece is placed at the image so as to create a parallel beam of small extent (pupil sized) that can be refocused by the eye.
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- Chapter
- Information
- Astronomy MethodsA Physical Approach to Astronomical Observations, pp. 130 - 174Publisher: Cambridge University PressPrint publication year: 2003