An Auxiliary Telescope waiting for sunset

The sun is setting at ESO´s Paranal observatory and the Very Large Telescope (VLT) is preparing for a night of observations. While the four 8.2-metre Unit Telescopes (UTs) are typically already opened at this time of the day, the four 1.8-metre Auxiliary Telescopes (ATs) need to wait until the sun is below the horizon to prevent sunlight from hitting the telescope mirrors. While the UTs can observe either individually or in a combined interferometric mode, the ATs are entirely dedicated to interferometry, a technique which allows astronomers to see details up to 25 times finer than with the individual telescopes.