but when we state that A 'equals' B , as well having to know what we mean by A and B we also have know what we mean by 'equals'. This section explores the role of observers; how different types of observ er see different things as being equal, and how we can produce algo rithms to decide on such equalities. It also explores how we go about writing specifications to which we may compare our SCCS designs. * The final section is the one which the students like best. Once enough of SCCS is grasped to decide upon the component parts of a design, the 'turning the handle' steps of composition and check ing that the design meets its specification are both error-prone and tedious. This section introduces the concurrency work bench, which shoulders most of the burden. How you use the book is up to you; I'm not even going to suggest path ways. Individual readers know what knowledge they seek, and course leaders know which concepts they are trying to impart and in what order.

This textbook describes the equipment, observational techniques, and analysis used in the investigation of stellar photospheres. Now in its fourth edition, the text has been thoroughly updated and revised to be more accessible to students. New figures have been added to illustrate key concepts, while diagrams have been redrawn and refreshed throughout. The book starts by developing the tools of analysis, and then demonstrates how they can be applied. Topics covered include radiation transfer, models of stellar photospheres, spectroscopic equipment, how to observe stellar spectra, and techniques for measuring stellar temperatures, radii, surface gravities, chemical composition, velocity fields, and rotation rates. Up-to-date results for real stars are included. Written for starting graduate students or advanced undergraduates, this textbook also includes a wealth of reference material useful to researchers. eBook formats include color imagery while print formats are greyscale only; a wide selection of the color images are available online.