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Places · Observatory
Vera C. Rubin Observatory
A 8.4 m survey telescope with a 3.2-gigapixel camera, built to photograph the whole southern sky every few nights for ten years and catalogue everything that moves or changes.
- Where
- Cerro Pachón, Chile
- Coordinates
- 30.24°S 70.75°W
- Since
- 2025
- On the map
- Show me
The sky from here
Measured at these coordinates the sky is zone 3: rural transition, which is Bortle 3–4 and a naked-eye limit of about magnitude 6.2–7.0. The Milky Way is clearly there but loses its detail near the horizon. Light domes are obvious in several directions.
Of the 110 Messier objects, 38 are an unaided-eye target from a sky this dark, 106 are comfortable in 10×50s and 106 in a 130mm reflector. You would have to get roughly 7 km west before the sky reaches Bortle 2.
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 89° 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 4 never rise.
Southern Pinwheel, Butterfly Cluster and Ptolemy's Cluster 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 30.24°S 70.75°W. 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 Vera C. Rubin Observatory?
Everything north of declination +60°. From 30.2°S that is a cap 30° in radius centred on the north celestial pole, which is 6.8% of the whole celestial sphere. It is out of reach permanently rather than seasonally: no time of year and no instrument brings it above the horizon. The matching 6.8% around the south celestial pole is the same geometry inverted, and never sets.
How many hours of true darkness does Vera C. Rubin Observatory get?
10 hours 57 minutes on the best night, around 21 June, falling to 6 hours 40 minutes around 21 December. The measure is astronomical darkness — the Sun a full eighteen degrees under — not simply the hours between sunset and sunrise. 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 Vera C. Rubin Observatory?
June and July, and the timing is the whole point. The core transits at midnight around 17 June everywhere, but at 30.2°S that is the depth of winter: the longest nights of the year, sitting underneath the galaxy at its highest. Northern sites get the same transit date during their shortest and least dark nights. It is the single biggest structural advantage a southern observatory has.
How far is Vera C. Rubin Observatory from the other sites on this map?
Gemini South is the nearest thing to it here — 1.2 km to the east. That is also the nearest other observatory, with the next one 10.0 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.