Today, the group of astronomers planning to build a large telescope, the Large-Scale Synoptic Telescope, announced that they had selected a site on which to build their telescope, a mountain in north-central Chile called Cerro Pachón.
The selection of a site is a vital part of building a telescope. It is not as simple as finding a dark mountain and bringing in the telescope parts, especially for modern, technologically-advanced telescopes. Some of the things we consider are the weather (How often is it crystal clear? What are the seasonal changes? How hard does the wind blow?), the seeing (how steady is the atmosphere?), the nearness of cities (causing light pollution and hurting our ability to see faint objects), the necessary infrastructure (Will we have to build 100 feet of roads or 100 miles of roads? Is high-speed Internet possible? What about water and food?), the altitude (if the altitude is too high, then we need to take care about the health of the astronomers and computers), and the overall economical and political situation (Will it cost too much to build? Is there endangered habitat we must be mindful of?)
These conditions, especially the last two, can change, so that a site that was deemed ideal (say, the dormant volcano Mauna Kea in Hawaii) may no longer be a workable solution due to past misunderstandings between Native Hawaiians, environmentalists, and astronomers.
Cerro Pachón already houses two telescopes, the Gemini 8-meter telescope and the SOAR 4-meter telescope, so from an economic and infrastructure point of view, it makes good sense to put the telescope there. We also have long-term experience with the weather there, and we understand the atmospheric stability. So today's site announcement makes sense.
How long until we can use this telescope? Only 6-10 years!