  Since the initial discovery of cometary charge exchange emission, more than
20 comets have been observed with a variety of X-ray and UV observatories. This
observational sample offers a broad variety of comets, solar wind environments
and observational conditions. It clearly demonstrates that solar wind charge
exchange emission provides a wealth of diagnostics, which are visible as
spatial, temporal, and spectral emission features. We review the possibilities
and limitations of each of those in this contribution.
