Optical secrets of the Very Large Telescope

The Very Large Telescope (VLT) at Paranal Observatory in northern Chile is the world's biggest optical telescope.

Run by the European Southern Observatory (ESO), it became fully operational in 2000 and is packed with cutting-edge instruments.

Stephane Guisard, an ESO engineer and a specialist in optics, explains how the VLT works.

Produced by Katia Moskvitch and Susannah Reid.