Section 2 - Introduction to CCD Cameras
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2.5.Electronic Imaging
Electronic images resemble photographic images in many ways. Photographic images are made up of many small particles or grains of photo sensitive compounds which change color or become a darker shade of gray when exposed to light. Electronic images are made up of many small pixels which are displayed on your computer screen to form an image. Each pixel is displayed as a shade of gray, or in some cases a color, corresponding to a number which is produced by the electronics and photo sensitive nature of the CCD camera. However, electronic images differ from photographic images in several important aspects. In their most basic form, electronic images are simply groups of numbers arranged in a computer file in a particular format. This makes electronic images particularly well suited for handling and manipulation in the same fashion as any other computer file.
An important aspect of electronic imaging is that the results are available immediately. Once the data from the camera is received by the computer, the resulting image may be displayed on the screen at once. While Polaroid cameras also produce immediate results, serious astrophotography ordinarily requires hypersensitized or cooled film, a good quality camera, and good darkroom work to produce satisfying results. The time lag between exposure of the film and production of the print is usually measured in days. With electronic imaging, the time between exposure of the chip and production of the image is usually measured in seconds.
Another very important aspect of electronic imaging is that the resulting data are uniquely suited to manipulation by a computer to bring out specific details of interest to the observer. In addition to the software provided with the camera, there are a number of commercial programs available which will process and enhance electronic images. Images may be made to look sharper, smoother, darker, lighter, etc. Brightness, contrast, size, and many other aspects of the image may be adjusted in real time while viewing the results on the computer screen. Two images may be inverted and electronically "blinked" to compare for differences, such as a new supernova, or a collection of images can be made into a large mosaic. Advanced techniques such as maximum entropy processing will bring out otherwise hidden detail.
Of course, once the image is stored on a computer disk, it may be transferred to another computer just like any other data file. You can copy it or send it via modem to a friend, upload it to your favorite bulletin board or online service, or store it away for processing and analysis at some later date.
We have found that an way to obtain a hard copy of your electronic image is to photograph it directly from the computer screen. You may also send your image on a floppy disk to a photo lab which has digital photo processing equipment for a professional print of your file. Make sure the lab can handle the file format you will send them. Printing the image on a printer connected to your computer is also possible depending on your software/printer configuration. There are a number of software programs available, which will print from your screen. However, we have found that without specialized and expensive equipment, printing images on a dot matrix or laser printer yields less than satisfactory detail. However, if the
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