Site Information

The Paranal Observatory is located on Cerro Paranal in the Atacama Desert in the northern part of Chile (map) and what is believed to be the driest area on Earth. Cerro Paranal is a 2,635-m high mountain, about 120 km south of the town of Antofagasta and 12 km inland from the Pacific Coast. The geographical coordinates are 24o 40' S, 70o 25' W.

Cerro Paranal was chosen because of its excellent atmospheric conditions and its remoteness. This ensures that the front-line astronomical observations carried out there are not disturbed by adverse human activities, e.g. dust and light from roads and mines.

Below is some information about the geography and environment of the Paranal Observatory:


Observational Information

Photometric Nights

The sky is clear or photometric about 75% of the night time. The fraction of photometric is about 25-30%. 

Seeing

The 50% percentile is 0.72" FWHM, see the seeing statistics from 2016 to 2023.

Wind Velocity Distribution

The median (50% percentile) of wind velocity at 30 m above ground is 6.2 m/s, see the statistics over the period 2000 to 2023.

 

Geographical Information

Altitude above sea level 2635.43 m
Distance from coast 12 km
Highest neighboring peak Cerro la Chira, 2569 m, 11 km to the NNE
Road distances 130 km to Antofagasta
Appr. 1200 km to Santiago
Appr. 600 km to La Silla
Telescope number Latitude Longitude
UT1 -24 deg 37 min 39.44 sec -70 deg 24 min 18.27 sec
UT2 -24 deg 37 min 37.80 sec -70 deg 24 min 17.39 sec
UT3 -24 deg 37 min 36.64 sec -70 deg 24 min 16.32 sec
UT4 -24 deg 37 min 37.36 sec -70 deg 24 min 14.25 sec
VST
-24 deg 37 min 34.79 sec -70 deg 24 min 14.27 sec
VISTA -24 deg 36 min 56.52 sec -70 deg 23 min 51.36 sec
Auxiliary Telescope Stations Latitude Longitude
A0 -24 deg 37 min 40.59 sec -70 deg 24 min 18.44 sec
A1 -24 deg 37 min 41.08 sec -70 deg 24 min 18.26 sec
B0 -24 deg 37 min 40.50 sec -70 deg 24 min 18.17 sec
B1 -24 deg 37 min 40.99 sec -70 deg 24 min 17.99 sec
B2 -24 deg 37 min 41.24 sec -70 deg 24 min 17.89 sec
B3 -24 deg 37 min 41.48 sec -70 deg 24 min 17.80 sec
B4 -24 deg 37 min 41.73 sec -70 deg 24 min 17.71 sec
B5 -24 deg 37 min 41.97 sec -70 deg 24 min 17.62 sec
C0 -24 deg 37 min 40.42 sec -70 deg 24 min 17.90 sec
C1 -24 deg 37 min 40.91 sec -70 deg 24 min 17.72 sec
C2 -24 deg 37 min 41.15 sec -70 deg 24 min 17.63 sec
C3 -24 deg 37 min 41.40 sec -70 deg 24 min 17.53 sec
D0 -24 deg 37 min 40.25 sec -70 deg 24 min 17.36 sec
D1 -24 deg 37 min 41.23 sec -70 deg 24 min 16.99 sec
D2 -24 deg 37 min 41.72 sec -70 deg 24 min 16.81 sec
E0 -24 deg 37 min 40.08 sec -70 deg 24 min 16.83 sec
G0 -24 deg 37 min 39.91 sec -70 deg 24 min 16.29 sec
G1 -24 deg 37 min 41.87 sec -70 deg 24 min 15.55 sec
G2 -24 deg 37 min 39.18 sec -70 deg 24 min 16.57 sec
H0 -24 deg 37 min 39.58 sec -70 deg 24 min 15.21 sec
I1 -24 deg 37 min 40.72 sec -70 deg 24 min 14.48 sec
J1 -24 deg 37 min 40.06 sec -70 deg 24 min 14.13 sec
J2 -24 deg 37 min 40.79 sec -70 deg 24 min 13.85 sec
J3 -24 deg 37 min 37.61 sec -70 deg 24 min 15.05 sec
J4 -24 deg 37 min 37.12 sec -70 deg 24 min 15.24 sec
J5 -24 deg 37 min 36.39 sec -70 deg 24 min 15.52 sec
J6 -24 deg 37 min 35.65 sec -70 deg 24 min 15.79 sec
K0 -24 deg 37 min 39.24 sec -70 deg 24 min 14.14 sec
L0 -24 deg 37 min 39.16 sec -70 deg 24 min 13.87 sec
M0 -24 deg 37 min 39.07 sec -70 deg 24 min 13.60 sec

Climate Information

Air pressure 750 mbar ±50 mbar
Density 0.96 kg/m³ Typ.
Temperature -8° to 25°C Measured 1985-1990
Temperature gradient during night -0.4°C/h Typ.
Typ. Humidity 5-20% Typ.
Rainfall <10 mm/year Typ.
Snow Once or twice per year Typ.
Ice buildup 5 cm Max.
Daily maximum 1120 W/m²
800 W/m²
Summer
Winter
Ozone

180 μg/m³

Max.
»Distribution >10 m/s 25% of the nights
  >20 m/s 50 nights per year
 
»Long term extremes 47.2 m/s 50 years return period
  50.7 m/s 100 years return period
  54.2 m/s 200 years return period
»Direction Wind rose
Pollution NO < 3 ppb Typ.
  NO2 < 2 ppb Typ.
  SO2 < 4 ppb Typ.

Seismical Information

Moderate earthquakes Some times per year Mg < 7.75
Operating basis earthquake (OBE):
»Peak horizontal acceleration 0.24 g Typ.
»Probability of excedance 50%
»Repetition period 25 years
»Magnitude 7.75 Richter
»Hypocentral distance 100 km
»Duration 65 s
Max. likely earthquake (MLE):
»Peak horizontal acceleration 0.34 g Typ.
»Probability of excedance 10 %
»Repetition period 100 years
»Magnitude 8.5 Richter
»Hypocentral distance 150 km
»Duration 200 s