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957 results in Observational Astronomy, Techniques and Instrumentation

Page 9 of 48

  • 1 - The Role of Radio Observations in Astronomy

  • from Part I - The Emission, Propagation, and Detection of Radio Waves
  • Bernard F. Burke, Massachusetts Institute of Technology, Francis Graham-Smith, University of Manchester, Peter N. Wilkinson, University of Manchester
  • Book:
    An Introduction to Radio Astronomy
    Published online:
    06 August 2019
    Print publication:
    22 August 2019, pp 3-14
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An Introduction to Radio Astronomy
  • 4th edition
  • Bernard F. Burke, Francis Graham-Smith, Peter N. Wilkinson
  • Published online:
    06 August 2019
    Print publication:
    22 August 2019
  • Radio astronomy is an active and rapidly expanding field due to advances in computing techniques, with several important new instruments on the horizon. This text provides a thorough introduction to radio astronomy and its contribution to our understanding of the universe, bridging the gap between basic introductions and research-level treatments. It begins by covering the fundamentals physics of radio techniques, before moving on to single-dish telescopes and aperture synthesis arrays. Fully updated and extensively rewritten, the fourth edition places greater emphasis on techniques, with detailed discussion of interferometry in particular, and comprehensive coverage of digital techniques in the appendices. The science sections are fully revised, with new author Peter N. Wilkinson bringing added expertise to the sections on pulsars, quasars and active galaxies. Spanning the entirety of radio astronomy, this is an engaging introduction for students and researchers approaching radio astronomy for the first time.

To Measure the Sky
  • An Introduction to Observational Astronomy
  • 2nd edition
  • Frederick R. Chromey
  • Published online:
    05 February 2019
    Print publication:
    20 October 2016
  • The second edition of this popular text provides undergraduates with a quantitative yet accessible introduction to the physical principles underlying the collection and analysis of observational data in contemporary optical and infrared astronomy. The text clearly links recent developments in ground- and space-based telescopes, observatory and instrument design, adaptive optics, and detector technologies to the more modest telescopes and detectors that students may use themselves. Beginning with reviews of the most relevant physical concepts and an introduction to elementary statistics, students are given the firm theoretical foundation they need. New topics, including an expanded treatment of spectroscopy, Gaia, the Large Synoptic Survey Telescope, and photometry at large redshifts bring the text up to date. Historical development of topics and quotations emphasize that astronomy is both a scientific and a human endeavour, while extensive end-of-chapter exercises facilitate the students' practical learning experience.

  • 20 - Time Applications

  • Dennis D. McCarthy, United States Naval Observatory, P. Kenneth Seidelmann, University of Virginia
  • Book:
    Time: From Earth Rotation to Atomic Physics
    Published online:
    01 October 2018
    Print publication:
    18 October 2018, pp 334-343

  • Summary

    The infrastructure of society depends critically on time and frequency services. Requirements for time and frequency exist with widely varying precision and accuracy. The applications include positioning and navigation services, time domain astronomy, intelligent transportation systems, communications, power grid, banking and finance, emergency services, water flow, science, religion, and general public needs.

  • 13 - Definition and Role of a Second

  • Dennis D. McCarthy, United States Naval Observatory, P. Kenneth Seidelmann, University of Virginia
  • Book:
    Time: From Earth Rotation to Atomic Physics
    Published online:
    01 October 2018
    Print publication:
    18 October 2018, pp 215-224

  • Summary

    Historically the second was considered a 60th of a minute, which was one 60th of an hour. A second based on the Earth’s variable rotation was impractical for modern timekeeping requirements. With the introduction of Ephemeris Time, the ephemeris second was defined in 1954 and revised in 1956 as 1/31 556 925.9747 of the length of the tropical year for 1900.0. The availability of atomic clocks made a more accurate and available second possible. So in 1968, the Système International (SI) second was defined as the duration of 9 192 631 770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the Caesium 133 atom. With such an accurate measure of the second, the meter was defined as the length of path traveled by light in vacuum during a time interval of 1/299 792 458 of a second. Other SI units are defined in terms of the second and meter. With improved accuracies of timekeeping based on optical frequency standards, a redefinition of the second is under consideration.

Page 9 of 48