Night Sky Brightness at Cerro Pachon

Cerro Pachon Model 1:

Our model 1 assumes a moderate population growth. Andacollo is a small mining center, with little growth potential both for population and mining; Ovalle is an agricultural service center (note we have added in the population of Monte Patria) that also has little growth potential. La Serena and Coquimbo have turned into major tourist centers in the past 10 years, but there is no industry, and our model shows the population growth slowing down over that experienced in the last 15 years. Official figures show Vicuna as having near-stagnant population, we have chosen to increase it rather drastically to allow for an increase of tourism-related activity in the Elqui Valley.

Here is the population model used (note that we have some new official predictions to 2005 that we will use to update these figures soon, but they make little difference to the results. They show Vicuna "flat", Andacollo increasing slowly, and the population of LaS-Coq. a little higher in 2000 than our figures).

Population growth:

Light per person model:

The light output per person in a "typical uncontrolled US city" is used as base, 1000L per person. Our estimates relevant to the cities here were based on installed street lighting figures for Vicuna and La Serena, population density compared to a US city (about a factor 5 smaller), the lack of any industry apart from tourism, the existence of only 2 malls for 250000 people, and the active steps being taken (successfully) to install environmentally friendly fixtures. However we realize our estimates are ad-hoc, and will re-do the calculations when better estimates are available.

Results:

Figure 4