Every stage of an observational project must be carefully planned and executed, from the preparation of the proposal to the execution of the observations themselves to the analysis of the data. In order to help astronomers at every stage of their observational research, ESO provides a number of tools for:

• Evaluating the time required to make the observations: ESO Exposure Time Calculators (ETCs)
• Determining when objects are best observed, including calculating airmass and other observing parameters: Ephemerides and Calculators;
• Assessing the current and near future weather prospects: Weather Images, Astroclimatology and Meteo Information;
• Accessing a number of astronomical archives and data catalogues: Archives and Catalogues.