Editing Very Large Telescope (section)

=== Auxiliary telescopes ===
[[File:From the Residencia to the Milky Way.jpg|thumb|Auxiliary Telescope, the Residencia and the heart of the [[Milky Way]]<ref>{{cite web|title=From the Residencia to the Milky Way|url=https://www.eso.org/public/images/potw1732a/|website=eso.org|access-date=7 August 2017}}</ref>]]

Although the four 8.2-metre Unit Telescopes can be combined in the [[#Interferometry|VLTI]], their observation time is spent mostly on individual observations, and are used for [[Astronomical interferometer|interferometric]] observations for a limited number of nights every year. However, the four smaller 1.8-metre ATs are available and dedicated to interferometry to allow the VLTI to operate every night.<ref name="vlthandout" />

The top part of each AT is a round enclosure, made from two sets of three segments, which open and close. Its job is to protect the delicate 1.8-metre telescope from desert conditions. The enclosure is supported by the boxy transporter section, which also contains electronics cabinets, liquid cooling systems, air-conditioning units, power supplies, and more. During astronomical observations the enclosure and transporter are mechanically isolated from the telescope, to ensure that no vibrations compromise the data collected.<ref name="esovlt" />

The transporter section runs on tracks, so the ATs can be moved to 30 different observing locations. As the VLTI acts rather like a single telescope as large as the group of telescopes combined, changing the positions of the ATs means that the VLTI can be adjusted according to the needs of the observing project.<ref name="esovlt" /> The reconfigurable nature of the VLTI is similar to that of the [[Very Large Array]].