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TAURUS can be used with one of a number of different CCD detectors, or with the IPCS--2 photon counting detector.
A number of factors need to be considered when deciding which detector is to be used, and these are discussed in detail elsewhere (e.g. La Palma Observers Guide). Basically, the CCD has a much greater efficiency than the IPCS, but also has a higher level of detector noise. For imaging observations, where the dominant source of noise is sky background rather than detector noise, the CCD will always be the detector of choice
The choice is more difficult for Fabry-Perot observations. The much narrower bandwidth of such observations means that detector noise will normally be an important factor. A major advantage of Fabry-Perot observations with the IPCS is also that it is possible to scan through a spectral line datacube very rapidly, averaging out variations in atmospheric transparency (see section ?). Thus the choice of detector depends both on the brightness of the source being observed, and on atmospheric conditions (difficult to predict in advance !).