TOPbases at the CDS

TOPbase, the Opacity Project atomic database, has been set up at the Centre de Donnees Astronomiques de Strasbourg (CDS), France, for general access via Internet. This database contains accurately calculated energy levels, f-values and photoionisation cross sections for astrophysically abundant ions. We briefly describe the physical model and computational method used, the atomic data specifications, the database management system and the network access arrangements. The new facility should be of value to the astronomical community