Point operations are important because astronomical images often span an extremely wide range of brightness, but important features in them often span a very narrow range of brightness. Alternatively, interesting features span a range of brightness too great for the limited range of hard copy or computer monitor. A well-chosen point operation can make hard-to-see features more visible by changing their original pixel values to a more appropriate range of pixel values.
In this chapter, you will learn where to find useful information tucked away in a long range of pixel values—and basic techniques that help you change the brightness scale of an image to display that information clearly. There are two parts to the task:
• identifying the range of interesting pixel values, and
• altering the pixel values for optimum display.
To see the information locked inside the image, you need to identify the range of pixel values that contains important information, and then transfer old pixel values to a new range. As you will discover, point operations are the simplest but most powerful tools for processing astronomical images.
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