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CCD ImagingCCD Imaging vs Film AstrophotographyCCD Imaging vs Film AstrophotographyBecause of a CCD chip’s greatly increased light-sensitivity compared to film, exposure times are typically much shorter. For example, a 2-minute unguided exposure of the Whirlpool Galaxy (M51) with a fairly inexpensive CCD camera will out-resolve photographic exposures of 30 minutes’ duration. The CCD imaging provides instant gratification—the image is immediately visible on your PC display as soon as it has been taken, without the normal darkroom work required of film. In addition film suffers from a phenomenon called reciprocity failure: the photographic emulsion becomes less and less sensitive as exposure time is increased. By contrast, the response curve of a CCD imager is linear: twice the exposure time yields exactly twice the results. |
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