A very large eye exam

Surrounded by the gleaming metal of one of ESO's Very Large Telescope’s Unit Telescopes, two engineers are carrying out maintenance work on the telescope’s complex and delicate optical systems. Similar to human eyes, the eyes of ESO’s Paranal Observatory must be constantly checked, maintained and tested in order to continuously provide the very best astronomical images.

The huge 8.2-metre Unit Telescope mirrors are housed in protective structures, ensuring that the delicate opto-electronic systems are sheltered from the harsh and dusty desert surroundings. But even with this level of protection, it still pays to spring clean the mirror from time to time! This is vital, as even the slightest contamination can distort the astronomical images received.

The fine dust particles of the Atacama desert not only lower image quality, but can also have an abrasive effect on the mirror’s surface. This means that not only does the mirror have to be cleaned, but it must be periodically recoated too. This episode of the ESOcast shows the process in action!

This image was taken by ESO Photo Ambassador Gerhard Hüdepohl, who formerly worked as an electronics engineer on Cerro Paranal.