European Spaceflight
Places · Observatory
Southern African Large Telescope
An 11 m segmented mirror held at a fixed tilt — cheaper to build than a steerable one, and it trades pointing freedom for aperture.
- Where
- Sutherland, South Africa
- Coordinates
- 32.38°S 20.81°E
- Since
- 2005
- On the map
- Show me
- More
- salt.ac.za
The sky from here
Measured at these coordinates the sky is zone 2: rural, which is Bortle 2–3 and a naked-eye limit of about magnitude 6.7–7.5. The Milky Way is structured and obvious. Light domes sit low on the horizon over distant towns, and the rest of the sky is genuinely dark.
Of the 110 Messier objects, 44 are an unaided-eye target from a sky this dark, 107 are comfortable in 10×50s and 107 in a 130mm reflector. There is nowhere darker worth driving to; this is already among the better skies on the planet.
Every night of the year reaches full astronomical darkness at this latitude; the Sun always gets its eighteen degrees below the horizon, which places much further from the equator cannot say.
The centre of the galaxy climbs to 87° at its best — high enough that the summer Milky Way is genuinely three-dimensional rather than a band low in the south. Of the 110 Messier objects, none are circumpolar and 5 never rise.
Butterfly Cluster, Ptolemy's Cluster and Southern Pinwheel pass close to the zenith from this latitude — an object at the zenith is being seen through the least air it will ever be seen through, and the difference against the same object low in the south is not subtle.
Against that, Bode's Galaxy and Cigar Galaxy never clear the horizon here at all. No amount of aperture or patience changes that; the only remedy is to travel.
Read at 32.38°S 20.81°E. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
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Questions
What part of the sky never rises at Southern African Large Telescope?
Everything north of declination +58°. From 32.4°S that is a cap 32° in radius centred on the north celestial pole, which is 7.8% of the whole celestial sphere. Nothing about the calendar or the aperture changes that — the cap is below the horizon at every hour of every night. Its mirror image, the same 7.8% around the south celestial pole, is circumpolar here and never goes down.
How many hours of true darkness does Southern African Large Telescope get?
11 hours 3 minutes on the best night, around 21 June, falling to 6 hours 21 minutes around 21 December. That counts only proper astronomical night, with the Sun eighteen degrees down; the merely-dark hours either side of it are longer. Every night of the year gets there eventually, which is the quiet advantage of not being any further from the equator than this.
When is the Milky Way best from Southern African Large Telescope?
Around 17 June, when the galactic centre crosses the meridian at local midnight — and because this is a southern site, that is also midwinter, with the longest and darkest nights of the year underneath it. The brightest part of the Milky Way reaches its highest point on the best nights available, rather than during a summer that will not go dark. That coincidence is most of the reason the world's large optical observatories are in the southern hemisphere.
How far is Southern African Large Telescope from the other sites on this map?
MeerKAT is the nearest thing to it here — 193 km to the north. That is also the nearest other observatory, with the next one 1,100 km beyond it. Measured as the great circle between coordinates, which is the shortest path across the surface and rarely the one you could travel.