CCD's allow far more detailed observation of the universe than the naked eye.
Since the telescope was invented four hundred years ago, it has worked primarily by focusing the light from distant objects on the user's eye, or on a film plate. However, in recent years, telescopes have been developed that make use of a charge-coupled device, or CCD, as an image sensor. This technology provides a number of advantages over older imaging methods.
What Is a CCD?
A CCD is an array of semiconductors mounted on a chip, much like a microprocessor. However, unlike the components of a microprocessor, the elements of a CCD are sensitive to light. Each element of a CCD develops a charge when light falls upon it, in proportion to the intensity of the light. Usually, the device can measure individual photons, and can do so over a very small area. It can also be set to discriminate between different frequencies (colors) of light.
How CCD's Are Used
CCD's are most widely used today in digital cameras of all types, from inexpensive point-and-shoots to high-end digital video cameras. With the CCD at the focus of the camera lens, where the film would previously have been, the camera records a digital image that can then be easily stored and manipulated. Digital images allow for immediate results without any additional processing, and make it possible to quickly alter or adjust the picture -- often immediately, within the camera itself.
Advantages for Astronomy
The application of CCD's to stellar photography has sparked a revolution in astronomy. Previous analog methods, such as the human eye or even the most sensitive film, were far too crude to allow any detailed analysis of the light coming through the telescope. With CCD's, however, it is possible to precisely measure the intensity and characteristics of the light striking each pixel. This means that astronomers can resolve smaller and more distant objects in far greater detail, providing more data with which to work -- and this can be done over a wide range of frequencies as well. And, since the images are digital, they can be immediately enhanced by imaging software and analyzed mathematically.
Combination and Collaboration
In addition to the benefits provided by the digital format, the nature of CCD images also lets astronomers benefit from computer networking. Images can be quickly shared with researchers around the world, creating fertile ground for scientific collaboration. Also, telescopes can be operated over the Internet, letting astronomers do important work without having to travel to remote locations; and CCD's allow telescopes to be connected together over long distances, which helps to increase the resolution of the images even further. Finally, the reliability and low cost of CCD's have revolutionized amateur astronomy, giving hobbyists the capability to create images that previously could only be made by professionals.
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