These pages provide access to the database of the Thirty Meter Telescope (TMT) site testing effort. It is our hope that they will become a useful tool for site testers, astronomers and other interested users around the world. The data are provided free to anybody with minimal usage and publication restrictions.

This data set represents a multi-year campaign at the five TMT candidates sites. The data have been gathered for, depending on the site and the type of data, periods between two and five years. Data were taken using identical sets of instruments on all five sites.

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Important: Please note that the data are not filtered for potentially invalid or corrupted points, as this would alter some of the statistics of the data set. Data that are invalid for one analysis might have to be included for another, so as to not arrive at misleading or incorrect results. We have therefore not excluded data from the database even if there are known problems with them. Please check out the Known Issues page for more information.

The TMT Project gratefully acknowledges the support of the TMT partner institutions. They are the Association of Canadian Universities for Research in Astronomy (ACURA), the California Institute of Technology and the University of California. This work was supported as well by the Gordon and Betty Moore Foundation, the Canada Foundation for Innovation, the Ontario Ministry of Research and Innovation, the National Research Council of Canada, the Natural Sciences and Engineering Research Council of Canada, the British Columbia Knowledge Development Fund, the Association of Universities for Research in Astronomy (AURA) and the U.S. National Science Foundation.