Abstract
Robotic instruments deployed by modern site-testing campaigns generate enormous amounts of information about essentially all relevant parameters of the atmosphere. Starting from relatively generic assumptions, it is possible to capture this wealth of information into a single figure of merit for each site, which simplifies some of the stages of the site testing process. This contributions presents two different formalisms that were used to evaluate the site-selection merit function for the E-ELT. Both formalisms rely on assumptions about the ways in which the telescope will be used -the science operations modes- but while one algorithm calculates figures of merit averaged over the whole site-testing campaign (typically 2 years), the other explores the variability of the observing conditions during the night, and from night-to-night during the campaign. We find that in general the two methods yield different results, signaling the importance of including variability as a key parameter to characterize astronomical sites for large telescopes operated in Queue-scheduling mode. However, the two best potential sites for the E-ELT are ranked best by both methods.
