The enclosure for the European Solar Telescope (EST)

The European Solar Telescope (EST) is a 4-m class solar telescope, which is currently in the conceptual design phase. EST will be located in the Canary Islands and aims at observations with high spectral, spatial and temporal resolution of the solar photosphere and chromosphere. The main purpose of the enclosure is to protect the telescope and instruments from severe weather conditions. An enclosure is also often needed for reducing wind buffeting on the telescope and primary mirror cell, but on the other hand enclosures are generally considered to degrade local seeing. In this contribution we will present the conceptual design of the enclosure for EST. Two different concepts have been studied in more detail: the first being a dome concept with vent gates to enhance local flushing, the other being a retractable enclosure, with an optional windshield. Technically both alternatives seem feasible, but we conclude that the retractable enclosure is the less risky solution, since it allows easier local seeing control and allows the use of a reflecting heat stop in the primary focus. A windshield is effective in reducing wind load on the primary mirror; although preliminary analysis indicate that there are feasible solutions to keep the deformation caused by wind buffeting within the requirements.