The altitude of Polaris (NCP) in particular equals the observer's latitude. Remember that Polaris' height is 0 degrees if you observe from the equator (0 degrees latitude) and 90 degrees if you observe from the north pole (latitude 90 degrees), and this is also true for intermediate latitudes.
Polaris can only be seen from the northern hemisphere. If you are living in the southern hemisphere, there is a chance that you might see another polar star called "Mickey". It is located near the south celestial pole and can only be seen by people who live at high southern latitudes where it doesn't freeze over during the winter months.
In fact, Mickey follows exactly the same path as Polaris across the sky each night. They are both stars that lie within the Milky Way galaxy, which is why they can be seen from everywhere on Earth with the exception of the poles.
People have been looking up at the sky for entertainment and knowledge since the first humans started building cities and having government systems. Over time, these activities became known as "astronomy" and scientists began to ask questions about how the universe works. One such object is Polaris, the center of the galaxy. It's important to understand that although it's possible to see other galaxies far away from Earth, no one has ever visited them.
Your latitude would be 30 degrees north if you observed Polaris at 30 degrees above the horizon. Now, the latitude is equal to 90-star altitude + star declination for any star that reaches its greatest altitude at a position lower than the observer's zenith. So, the latitude of Polaris is also 90-star altitude + star declination.
In general, the latitude of a celestial object is equal to its altitude above the horizon. The altitude is the distance between the center of the earth and the point on its surface where the object is located. For example, the latitude of a celestial body is the angle between it and the equator of the earth. If you were standing at the equator and looked toward one of the poles, you would see a body in the sky at exactly 90 degrees west or east of south. This is because the pole is directly over each capital city on Earth.
Celestial objects such as stars and planets appear to move against the backdrop of the night sky because they are actually not fixed but rather wander across the face of the earth or other part of the solar system. It is this apparent movement that causes them to rise over one area and set over another.
This means that Polaris' height will nearly never correspond with an observer's latitude. To view Polaris at an altitude of 0 degrees on the horizon (as visible at the equator), an observer would have to be an infinite distance away. Simple trigonometry explains why. The angle between a vertical line and the horizon is called the zenith angle. At the North Pole, all horizontal lines are at a 90-degree angle with the Earth's surface. Thus, the zenith angle is 90 degrees, and the Sun appears directly over its position. At the South Pole, all horizontal lines are at a 180-degree angle with the Earth's surface.
At any other point on the globe, the zenith angle varies from zero at the Equator to 90 degrees at the Poles. As the zenith angle increases beyond 90 degrees, it becomes more difficult to see the Sun because it is no longer directly overhead. Instead, it is seen at a lower elevation than expected, which is what causes the Sun to appear low in the sky at high latitudes.
Polaris is only visible as a faint star near the constellations Cygnus and Draco. From north of the equator, look south around midnight during the summer months for a glimpse of this bright star.
In the scale figure below, you can see that Polaris will have the right matching altitude angle from latitude N 45 deg, but not from anyplace else except the North Pole if it is positioned at a height of 3,100 miles above a flat earth (as an example). An example of Polaris' altitude angles on a flat earth. The red line shows where the altitude angle is 0 degrees; the blue line shows where it is 90 degrees.
So if you were standing at latitude N 45 deg watching Polaris rise (or set), its altitude would look like this: 43 degrees at midnight, 50 degrees at noon, 33 degrees at 6 p.m., and 8 degrees at 9 p.m.. It would always be seen as rising over time because the flat surface of the earth gets closer to it as time goes by.
Polaris does not reach all the way to the horizon at any time or place on a flat earth because there is no horizon. Instead, it keeps getting further and further away from you as it rises.
This is very different from how things work on a globe earth. On such a globe, when you are at latitude N 45 deg you can see Polaris reach half way to the horizon at midnight, three quarters of the way at noon, half way again at 6 p.m., and completely visible at 9 p.m..
As a result, the angle formed by the northern horizon and Polaris equals the observer's latitude. Polaris, for example, is on the northern horizon as viewed from the equator (0 degrees latitude). It is also on the northern horizon as viewed from 45 degrees north (90 degrees latitude) and from 60 degrees north (120 degrees latitude). Thus, the angle between itself and the northern horizon is constant for all locations around the earth where it can be seen.
Polaris isn't the only star that forms an angle with the northern horizon. There are actually three stars that lie along the celestial equator: The Earth's shadow will find these stars at 90 degrees east or west of north. These are called the Pole Stars. Over time, the position of one of them, Polaris, has changed due to precession. However, the other two stars have always been in the same place relative to the North Star!
The fact that there are always three stars along the celestial equator means that there are always three directions on the sky that are equal distance from the center point. These directions are called "directions south", "east" and "west".
From here on out, we'll refer to these directions as "south", "east" and "west".