It stares at a fixed patch of sky, watching a field of more than 150, 000 stars for the tiny dips in starlight that occur if an orbiting planet passes between a star and the telescope.

BBC: Exoplanets near red dwarfs suggest another Earth nearer

In this image taken of a small patch of sky in the constellation of Ursa Major, countless galaxies are recorded.

BBC: Herschel space telescope to go blind

Financial analysts see a patch of blue sky should car sales recover.

FORBES: What GM Will Look Like, If It Survives

And we, as consumers, face these sheer walls, smooth as glass, edifices of obsidian, crystal, and silver that reach up to the sky, blocking all but a tiny patch of light.

FORBES: Dystopia In The Lovely Walled Gardens

Find this orientation by looking through the crystal at the sky at a time when you can see the sun, mark the sun's direction on the crystal, and your mark will always point towards the sun when you match the beams from even a tiny patch of blue in an otherwise overcast sky.

ECONOMIST: How Norsemen found their way round in cloudy weather

If you're unlucky enough for your local patch of sky not to have enough satellites, or you're in a downtown where the signals are blocked, you're not going to get accurate navigation.

CNN: Why your trusty GPS sometimes fails you