These lectures review the use of morphological, photometric and kinematic observations to study the structure and evolution of galaxies. The emphasis will be on physical problems and on observational ways of attacking them. A review of results will be given, but this will in general be incomplete, especially for subjects with recently published reviews. This paper complements such reviews as much as possible, although some overlap is unavoidable. Sections 2-4 discuss morphology, surface photometry, and kinematics of unbarred galaxies. Section 5 then discusses barred galaxies in special detail, in part because they provide useful examples of morphological and kinematic techniques. Bars also lead to the simplest and most direct demonstrations of internally driven secular evolution; the widespread importance of such processes is becoming increasingly clear (see also Binney 1982a).
It is important to understand that this is an especially opportune time for observational studies of galaxy structure. Scientific progress rarely proceeds at a uniform rate. Technical advances can lead to sudden, large increases in the amount and quality of data available (see Harwit 1981a, b). On the conceptual side, physical understanding tends to be a threshold phenomenon: progress seems slow until the accumulation of apparently unconnected results reaches a point where "many things suddenly fall into place". Either of these events can precipitate a period of rapid progress. Both are doing so now. Technical advances include efficient, computer-controlled microdensitometers which now allow us to study photographic plates accurately and in detail. More important, powerful detectors are available which provide two dimensional digital photographs of large extent. For example, well-designed cameras based on CCDs (charge coupled devices) are easier to use than conventional techniques and provide data of much higher accuracy. CCDs also have quantum efficiencies 3 times as high as image tubes and 30 times as high as photographic plates. Equally important is the widespread development of two-dimensional image processing facilities, which allow us to efficiently exploit the large volumes of data produced by digital detectors. All of these factors contribute to a radical increase in the amount of information available, and in our ability to ask difficult observational questions. An involvement in these developments is turning into a prerequisite for state-of-the-art observational research. The result can realistically be described as a revolution in our understanding of galaxy structure and evolution. This is still in its early stages. For example, we are still far short of having complete, self-consistent models. However, there is cause for optimism that the technical advances of the past decade have begun the process of making the study of galaxies as physically rigorous as the study of stars is today.