Firstly select which telescope/detector combination gives the required field of view combined with adequate sampling. Table gives the scale and field size for each combination of focal station and CCD.
The pixel size required to give adequate sampling is rather difficult to determine, and depends upon the application. For faint stellar photometry it is important to sample the images well; packages such as DAOPHOT work best if the pixel size is a quarter of the point source FWHM or less. For surface photometry of extended objects the sampling can be coarser; in this case the resolution will not be degraded significantly as long as the pixel size is a half of the stellar FWHM or less.