Accurate atomic data have always been essential for the realistic modelling of astrophysical plasma. However major improvements in the last few years in the variety and quality of the observational material available from both ground and satellite based instrumentation has made this requirement even more stringent. Over the past decade, several computer codes have been developed to calculate such data, including CIV3 and RMATRX, which are used for generating radiative rates, and electron impact excitation rates, for atoms and ions respectively. Results from these codes have been applied to the analysis of a wide range of astronomical observations.

However probably the most successful application of the atomic data have been to the development of electron density and temperature diagnostic emission line ratios for astrophysical plasmas, including the solar transition region/corona and late-type stellar atmospheres. Many diagnostics have been calculated over the past few years and applied to solar UV, EUV and X-ray solar spectra (obtained with the Solar Maximum Mission and P78-1 satellites, the S082A,B and S-055 instruments on board SKYLAB and the High Resolution Telescope and Spectrograph) on board SPACELAB 2), as well as UV observations of late-type stars obtained by the International Ultraviolet Explorer and Extreme Ultraviolet Explorer satellites. Several of these will be used by my students in their solar work involving data from the The CDS and SUMER onboard the SOHO and EIS onboard Hinode.