| 书目名称 | Telescopes and Techniques | | 副标题 | An Introduction to P | | 编辑 | Chris Kitchin | | 视频video | | | 概述 | This carefully structured introduction to astronomical instruments can be used by first-year students or amateur astronomers.Self-test questions and exercises - with answers - are provided.Includes on | | 丛书名称 | The Patrick Moore Practical Astronomy Series | | 图书封面 |  | | 描述 | The modern aspiring astronomer is faced with a bewil dering choice of commercially produced telescopes, including all the designs considered in the preceding chapter. Yet only four decades ago the choice for a small telescope would have been between just a refrac tor and a Newtonian reflector. That change has come about because of the enormous interest that has grown in astronomy since the start of the space age and with the mind-boggling discoveries of the past 30 or 40 years. Except for some of the very small instruments which are unfortunately often heavily promoted in general mail order catalogues, camera shops and the like, the optical quality of these commercially pro duced telescopes is almost uniformly excellent. Although one product may be slightly better for some types of observation, or more suited to the personal cir cumstances of the observer, than another, most of them will provide excellent observing opportunities. The same general praise cannot be applied, however, to the mountings with which many of these telescopes are provided, and those problems are covered in Chapter 6. | | 出版日期 | Book 20032nd edition | | 关键词 | Telescopes and observing; astronomy; instruments; photometry; spectroscopy; telescope | | 版次 | 2 | | doi | https://doi.org/10.1007/978-1-4471-0023-2 | | isbn_ebook | 978-1-4471-0023-2Series ISSN 1431-9756 Series E-ISSN 2197-6562 | | issn_series | 1431-9756 | | copyright | Springer-Verlag London 2003 |
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Types of Telescope |
Chris Kitchin |
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Abstract
Until recently, the invention of the telescope was generally attributed to a Dutch spectacle maker called Hans Lippershey (or Lippersheim, 1570?–1619). He worked at Middleburg on the island of Walcheren, some 60 km north-west of Antwerp. The probably apocryphal story has it that in 1608 his children discovered, while playing with some of his spare lenses, that one combination made a distant church spire appear much closer. The exact combination oflenses they and he used is no longer known, but it is likely to have been a pair of converging lenses. An example of the resulting telescope was duly presented to the States-General, Prince Maurice. The news of the discovery spread rapidly, reaching Venice and Galileo only a year later. The details received by Galileo just concerned the effect of observing with the instrument, and not the details of its design. However, he had at that time been working extensively on optics, and in a few hours was able to design an optical system that reproduced the reported distance-shortening effect of the instrument.
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Telescope Optics |
Chris Kitchin |
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Abstract
Telescopes normally use two lenses and/or mirrors to produce a magnified, and in the case of point sources, brighter image. There are many different designs, the basic properties of several of those more commonly encountered having been discussed in Chapter 1. In this chapter we take a closer look at the details of some of those designs.
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Modern Small Telescope Design |
Chris Kitchin |
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Abstract
The modern aspiring astronomer is faced with a bewildering choice of commercially produced telescopes, including all the designs considered in the preceding chapter. Yet only four decades ago the choice for a small telescope would have been between just a refractor and a Newtonian reflector. That change has come about because of the enormous interest that has grown in astronomy since the start of the space age and with the mind-boggling discoveries of the past 30 or 40 years. Except for some of the very small instruments which are unfortunately often heavily promoted in general mail order catalogues, camera shops and the like, the optical quality of these commercially produced telescopes is almost uniformly excellent. Although one product may be slightly better for some types of observation, or more suited to the personal circumstances of the observer, than another, most of them will provide excellent observing opportunities. The same general praise cannot be applied, however, to the mountings with which many of these telescopes are provided, and those problems are covered in Chapter 6.
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Positions in the Sky |
Chris Kitchin |
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Abstract
Most people are familiar with the idea of plotting a graph. This is one example of a coordinate system, the . and . coordinates (abscissa and ordinate) providing a means of specifying the position of a point within the two-dimensional surface occupied by the graph. It is a simple extension of the idea to give completely the position of an object in space using three coordinates, ., . and . (Figure 4.1).
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Movements of Objects in the Sky |
Chris Kitchin |
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Abstract
Objects in the sky, including the so-called “fixed” stars, actually move in various ways, some quite complex, for a variety of reasons.
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Telescope Mountings |
Chris Kitchin |
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Abstract
Telescope mountings divide into two distinct sections. The first is the set of mechanical components that hold the optics of the telescope in their correct relative positions, and allow them to be collimated and to be focused. This section is normally called the telescope tube, and reference is made to it in Chapters 1,2,3 and 8. Here, therefore, we are concerned with the second section, which is the set of mechanical components that enables the telescope tube and the optics to be pointed at the object to be studied, and in most cases then to compensate for the Earth’s rotation (i.e. to track the object) automatically. Reference to this section of the mounting has also been made elsewhere (Chapters 1,2, 3, 4, 5 and 8), but we now look at its specifications in more detail. In this chapter, we shall use the term . to refer only to this second section from now onwards.
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Electromagnetic Radiation |
Chris Kitchin |
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Abstract
Almost all our information in astronomy is obtained by the electromagnetic radiation travelling from the object to the observer. Apart from those few objects within the solar system that we have been able to investigate directly, cosmic rays, neutrinos and, in due course, gravity waves are the only other information carriers likely to tell us about the universe as a whole. The electromagnetic radiation wave consists of a magnetic wave and an electric wave whose directions are orthogonal, and which vary sinusoidally. The frequency of the sinusoidal variation is called the frequency of the wave and denoted usually by .. The separation of successive crests or troughs gives the wavelength, λ. The product of . and λ gives the wave’s velocity. In a vacuum this has a constant value, denoted by ., of 299 792 500 m s..
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Visual Observing |
Chris Kitchin |
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Abstract
In this chapter it is assumed that the reader has access to a small to medium-sized telescope (10–30 cm, or 4–12 inches) on an equatorial mount, with a motor drive, and intends to use it for visual work. If the telescope is not on an equatorial mounting, then most of the observations will still be possible but will generally be more difficult. If the telescope is smaller than 10 cm, then many of the fainter objects will be difficult or impossible to see. If the telescope is larger than 30 cm — congratulations! Other types of observing such as imaging with photographic emulsion or CCD, photometry and spectroscopy are considered in later chapters. Visual work is an aspect of imaging (Chapter 9); nowadays it is sometimes regarded as inferior to methods providing a permanent record — it certainly can be a subjective process (see later), and is limited in the wavelengths and intensities detectable.
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Detectors and Imaging |
Chris Kitchin |
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Abstract
The front line detectors for almost all astronomers are their own eyes. For many, especially when using smaller telescopes, these are also the only detectors. The eye, or more particularly vision, which is the result of the eye and brain acting in concert, is, however, a very complex phenomenon, and some knowledge of its peculiarities is essential for the observer. Thus reference has already been made in Chapter 8 to averted vision, the effect of high contrasts (known as irradiation), and the combination of subresolution features (Martian canals). The structure of the whole eye (Figure 9.1) is well known from school, and need not be considered further here. It is the structure of the eye’s detector, the retina, that is of importance.
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Data Processing |
Chris Kitchin |
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Abstract
Observing time on major telescopes is usually allocated to individual astronomers or groups of astronomers a few nights at a time, and at most three or four such sessions might normally be available over a year. This does not mean that the astronomers concerned can relax for the other 50 weeks, but it is a measure of the relative efforts required at a research level in obtaining the data in the first place compared with the processing then needed. Usually many multiples of the time spent observing have to be spent afterwards working on the data (photographs, CCD images, spectra, photometric measurements, astrometric measurements, etc.) in order to get it into the finally desired form.
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Photometry |
Chris Kitchin |
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Abstract
Photometry is the process of determining intensity or magnitude of or within the original object. It most commonly involves measurements of point sources or near-point sources like stars and planets, but it can also involve measuring the integrated intensities or magnitudes of more extended objects. Any of the detectors discussed in Chapter 9 can be used for photometry. The CCD and p-i-n photodiode are, however, the most straightforward because they have linear responses, and their outputs can be converted directly into magnitudes using Equation (8.5). The eye and the photographic emulsion are non-linear detectors and their responses are therefore more complex to convert into magnitudes. The visual estimation of magnitude having already been discussed in Chapter 8, we shall consider CCD and photographic photometry further below.
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Spectroscopy |
Chris Kitchin |
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Abstract
Spectroscopy is the study of the way that the brightness of an object varies with wavelength. . photometry gives some information of this type (Chapter 11); the STJ detector (Chapter 9) also has an intrinsic spectral resolution (see below) of a few tens of nanometres in the visual region. But, by common consent, spectroscopy normally has a spectral resolution of 1% or better, photometry a spectral resolution of 1% or worse. Although it is the most fruitful technique available to astronomers, capable of yielding information on temperatures, compositions, luminosities, pressures, magnetic fields, levels of excitation and ionisation, surface structure, line of sight velocities, turbulent velocities, rotational velocities, expansion/contraction, binarity, and, less directly, distances, masses and ages, spectroscopy has generally found little favour among users of smaller telescopes. This is almost certainly because of the long exposures normally required, even on large telescopes, in order to obtain a spectrum.
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发表于 2025-3-21 19:03:01
