So what's visible to an astronomer at a dark site in Spain?
There are two parts to the answer. The first is that since the sky here is much
darker and more transparent (contains fewer particles and pollutants) than in
an urban environment, astronomers can see a great deal more detail. The other part is
that as the location is closer to the equator than places in northern europe,
or the northern USA & Canada, you can observe features that never rise above the horizon.
This also means you get more seasonal variation than at locations further north.
(There is another attribute - with the sole exception of Mt. Jabalcon, the horizon around CdN is reasonably flat and low. This means that the sky is
visible down to about 3° to the south (as shown on the right-side chart) and not much higher in other directions. Although it's perfectly possible to get such low horizons elsewhere, it's
not something I have in the built-up SouthEast of England.
If you want to visualise this, I have a panorama of the view from Cuevas del Negro as a
at this link.
Look at the two charts below. The one on the left compares the whole of
the sky as it looks from Cuevas del Negro and when you move the mouse onto the
image, how it looks in Oxford (a nearby town to me in England).
The pink dot shows the position of Polaris - which the whole sky rotates around.
On the right is a chart of the sky, created from Stellarium
with my Cuevas del Negro landscape superimposed. It shows the southern
part of the sky. You'll see what difference being 14° further south makes.
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Move the mouse onto the image for the Oxford full sky
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See how everything moves lower, and Centaurus disppears completely
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