Places · Observatory
Roque de los Muchachos
A ridge above the clouds carrying the 10.4 m Gran Telescopio Canarias, the largest single-aperture optical telescope in operation, and the northern Cherenkov array.
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 15 km north-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 reaches 32° at its highest, which puts the brightest part of the Milky Way clear of the horizon murk without ever being overhead. Of the 110 Messier objects, 3 never set from here and every one of them rises at some point in the year.
Triangulum Galaxy, Ring Nebula and Pleiades 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.
Bode's Galaxy and Cigar Galaxy never set from this latitude, so they are available on any clear night of the year rather than for one season of it.
Read at 28.76°N 17.89°W. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
Nearby
Questions
What part of the sky never rises at Roque de los Muchachos?
Everything south of declination −61°. From 28.8°N that is a cap 29° in radius centred on the south celestial pole, which is 6.2% 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 6.2% around the north celestial pole is the same geometry inverted, and never sets.
How many hours of true darkness does Roque de los Muchachos get?
10 hours 53 minutes on the best night, around 21 December, falling to 6 hours 52 minutes around 21 June. 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 Roque de los Muchachos?
Mid-June at its highest, with a workable season either side of it running from about May into September. Because 28.8°N keeps full astronomical darkness all year, the whole of that season is usable, which is not the case for observers much further from the equator, who lose the peak of it to summer twilight.
How far is Roque de los Muchachos from the other sites on this map?
Teide Observatory is the nearest thing to it here — 144 km to the east. That is also the nearest other observatory, with the next one 3,010 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.