A large fraction of the Observatory staff is involved in surveys of extragalactic objects, As an aid to observational cosmologists, de Ruiter has made available (on the WEB) a collection of cosmological formulas. For a number of models (the standard Friedmann model, flat models with non-zero cosmological constant, and some more exotic ones) distances, volumes and look-back times are given as a function of redshift. In many cases the solutions are given in analytical form. The compendium can be found on the WEB . Some of these surveys are ongoing long-term projects, but quite a few have started only recently, or will start in the near future, and will require telescope time with new generation optical telescopes like the VLT.