This is Julie's description of our visit to Paranal.
" About 60 kms from Antofagasta we turned right towards Taltal and Paranal. This road was the same as we took before [when we were going north], and it is a really good road so we made good time. This is where the valley has no vegetation at all, is very gravelly with bigger rocks scattered over it, and the hills on either side are likewise bare. The road was pretty straight with the occasional gentle curve.
The turn-off to Paranal is about 65 kms from highway #5 and we arrived there about 12:30pm. We turned right and headed up the road to Paranal (bitumen) which climbed quite steeply, winding back and forth up the mountain. When we arrived at the gate, we were still very early, although there were a couple of other cars there waiting for the tour.
The tour started just after 2pm. There were 11 car-loads of people, and we all had to drive through the gate and park just on the other side, all facing the same way. The visitor’s centre is there (we could have walked from the first car park) and we watched a video about the ESO generally, and Paranal specifically. It was in Spanish with English subtitles, so I didn’t get to see the photography much. From there the Spanish speakers were taken out while the 4 English speakers (us included) had the rules explained to us before we were issued with hard hats to be worn in the telescope buildings.
Back in our cars, we snaked our way up the last hill to the levelled area where the four 8.2m telescopes are. There are also four small 1.8m telescopes. The hill they are built on used to be 2628m above sea level, but they took the top 28m off to level the site. Again we all parked facing the same way before we were divided into 3 groups each with our own guide. Our group was the English speaking group, and 3 others joined us (from Belguim – the others were from England {American and Norwegian originally}). Our guide’s name was Hernan Julio and he spoke good English. He is an amateur astronomer (lives in La Serena and comes up by bus 2 weekends a month to do tours). He also takes VIP tours for people who want to look at the sky at night.
The first place we went was inside one of the 8.2 telescope buildings [Melipal], where we saw the mechanism and mirrors, the camera and infra-red extras. We also saw the secondary mirror and a third 45o mirror, how the telescope opens and the floor turns. It was quite cold in the building (Hernan said maybe 5 deg C) as they keep the telescope at the same temperature as the air was the night before. From there we went outside and saw the site of the new 39m telescope the ESO is building which will be lots bigger than Paranal and this is one is the biggest optical telescope in the world at present. The site is on the other side of the valley, on a mountain [Cerro Armazones] that is about 400m higher than Paranal, close to a test telescope that is already there. This will be called the E-ELT telescope (European Extra Large Telescope, while Paranal is called the VLT –Very Large Telescope). Next we visited the control building where a few people were working at computers getting the telescopes ready for the night. We were allowed to sit at the desks for photos!
Our guide then took us back to the cars and just our 3 cars drove down the hill back to look inside the accommodation building, which looks to be underground, but actually follows the level of the ground and is 3 storeys high on the south western side. It was designed so that no light would shine out at night. It has a huge central round area full of plants, with a dining area overlooking a large swimming pool. The building has 108 rooms for staff and visiting astronomers. Everyone wants to stay there, but Hernan said that he doesn’t get to sleep there, but in a “container” type building which was left there after they finished filming for the James Bond movie, Quantum of Solace.
From there we went back to the visitor’s centre where we had time to look at and read the displays. We were just finishing when the first of the Spanish groups arrived, and the place was full of people again, so it was good to have had it to ourselves for a while.
The four big telescopes at Paranal can be used either individually or together to form a 16m telescope (equivalent). The four small telescopes can also be used in conjunction with the 4 big ones, to form a 200m telescope (equivalent resolution). Apparently though, the machine to complete this is still being built in Europe, so the most they can join at present is three big telescopes (don’t know about the small ones). The light from the telescopes is sent through a series of underground tunnels, to one central interferometer place where the light is all joined together before going to the control building. The four big ones collect the light for the images and the four small ones give the resolution to the images.
Once a year the mirrors have to be resurfaced with aluminium and there was a crane near one building which was getting ready to take the mirror out. The amount of aluminium used for the 8.2m telescopes is less than they use in a can of coke – it is thinner than a human hair – pretty impressive.
The astronomers who come to Paranal generally only come from one of the 15 countries that are part of the ESO group, although Chilean astronomers have 10% of the time allocated to them. Astronomers have to apply for time to use the telescopes, and they get 5 times as many requests as they can approve so only the “best” projects get to use the telescopes. Astronomers are only allocated between 3 and 5 nights. We were told they get 350 clear nights per year, so I guess they are pretty much guaranteed not to lose out because of bad weather. It hasn’t rained at Paranal for several years although last year in July they had snow (about 20 cms) and they get some snow most years.
The site at Paranal was levelled in 1990 and the last of the 4 small telescopes arrived in 2006. One of the main areas of study at Paranal has been exoplanets, planets which orbit other stars, also very distant galaxies.
It was just after 5pm when we finished in the visitor’s centre and we still had over 100 kms to go to Taltal. Once we got back on the main road, there was about 20 kms still along the high valley before we started to go down to the coast at Paposo. It was much quicker going down the hill [we drove up on the way north] and the 30 odd kms went by quickly! From the bottom of the hill we had about 55 kms to drive south along the coast. The fog was still there even at this time of the day, but it wasn’t as thick, and we didn’t get into it until lower down. It was interesting to note that at the level where the fog started, there were also the beginnings of a few straggly grasses growing on the hills."
http://www.eso.org/public/teles-instr/vlt.html