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If you have ever planned a trip by looking at the lunar calendar before the flight calendar, this destination is for you. A good sky does not depend only on there being no cities nearby: it depends on three physical variables that rarely coincide, and here all three coincide at once.
01 The three factors, all at once
The first factor is cloud, and here it is almost a non-factor. The city accumulates 3,490.3 hours of sunshine a year and more than three hundred clear days. No month falls below 243 hours. For anyone planning observing nights, that means the chance of losing an outing to cloud is very low.
And the third is altitude. The city sits at about 1,700 metres on the Khomas Highland plateau, and the country's interior stays high. The less atmosphere there is above you, the less absorption and the less turbulence between the telescope and the star. It is why observatories are put on mountains.
02 The gold-tier reserve
The nearest communities are some ninety kilometres away. That emptiness is what produces one of the darkest skies measured to date.
The real destination of a sky trip here is not the capital: it is the NamibRand nature reserve, in the country's southwest. In May 2012 it was declared an International Dark Sky Reserve, the first in Africa, and at 'gold' tier, the strictest category, reserved for skies with the least impact from artificial light.
The figures behind it are of an uncommon scale. The reserve covers more than 2,150 square kilometres, close to the area of Luxembourg, and the nearest communities are some ninety kilometres away. That isolation is what makes it one of the darkest skies measured so far.
03 When to come
The good window runs from May to September, and it is so clear it hardly admits argument. In those five months precipitation runs from 3.1 millimetres in May to 0.0 in July, with 0.5, 0.0, 0.3 and 2.1 in June, July, August and September. In July, on average, it does not rain on a single day of the month.
Within that span, August and September are the best: 319.3 and 297 hours of sunshine, with relative humidity at 24 % and 21 %, its two annual minimums. September adds the advantage that nights are already up to a mean low of 12.7 degrees, against August's 8.5.
And above the month is the moon, which is the variable that really governs this kind of trip. It is worth lining the observing nights up with the new moon and accepting that this may shift the whole trip by a week or two. With a climate calendar this stable, that margin costs nothing.
04 What has to be accepted
The first limit should be said early to avoid the misunderstanding: you do not see the good sky from Windhoek. It is a city of almost half a million people, with its own lighting and its own glow. Everything that makes this destination exceptional happens once you leave it.
The second is distance, and it is considerable. The NamibRand reserve is some 400 kilometres southwest of the capital, and the sources giving the higher figure say around 500. That means road, vehicle and several days: it is not a one-night excursion from the city.
With those three points accepted, the proposition fits a very defined profile: one or two nights in the capital to get organised, and seven to ten days on the road through a high, dry, cloudless country, with the nights arranged around the new moon. Few destinations offer the three sky variables aligned like this.
