Intro and Visual description
Use the pointer stars of the Big Dipper to find Polaris, the tip of Ursa Minor’s tail. The whole sky seems to rotate around Polaris once a day, since it is located near the north celestial pole. The two other bright stars of Ursa Minor represent the far edge of its dipper, and lie nearer to the Big Dipper.
You can learn, as did ancient sailors and western cowhands on the night watch, to tell the time of the night by the position of the Big Dipper. Due to the daily rotation of the earth, the dipper rotates around the north star every twenty four hours. As the night hours pass and the Earth turns on its axis, the stars turn in circles around Polaris, which appears to stand still. Some constellations are close enough to Polaris that they never set below the horizon. These are the circumpolar stars. Most stars are farther away from Polaris, and fall below the horizon. These appear to rise in the east, cross overhead, and set in the west, much like the Sun.
and climb the heavens, and go,
And thou dost see them rise,
Star of the Pole!
and thou dost see them set,
Alone, in thy cold skies,
Thou keep’st thy old unmoving station yet.
From ancient times sailors have known that the altitude of Polaris above the horizon is the same as one’s latitude on Earth. For example, my latitude in central Oklahoma is 35 degrees north, and I find Polaris 35 degrees above the northern horizon. Similarly, to sail west at a constant latitude Columbus kept the north star at a constant altitude above the horizon.