The text has been written on several levels in the hope that a wide range of people will be able to find something in it for them. In addition, the flow of the book has been arranged to be more useful as a college text on astronomical instruments and techniques by using electronic imaging as a unifying theme, the aim is to provide a simplified, broad-based introduction to astronomical detectors and instrumentation that would be suitable for advanced undergraduate students and new graduate students who need a background in observational methods.