Everyone knows that light pollution is the main obstacle to stargazing, so if you can, you should stay as far away from the city as possible. The closer to the sky, the more open place is of course the first choice for stargazing.

If you can't, at least turn off the lights in your room.

In less cloudy weather, staring at the starry sky for a long time, you will definitely see more and more stars. In addition, it is best not to stargaze when the moon is full. The light reflected by the moon will inevitably dim the stars.

But remember, all we see is the light from the stars. Some stars are too far away from us, traveling tens of millions of light-years to enter our line of sight, and the stars themselves may have disappeared into the universe.

When we look at the stars, we are actually looking at the past.

1. The North Star we are most familiar with

Polaris is not the brightest star in the sky. The brightest star is probably our closest planet, Venus, which does not emit its own light. But the all-important North Star in the chart has been helping us find our way for countless years.

The only star in the sky that doesn't change position over time is Polaris.

The methods we are most familiar with to locate the North Star are two methods introduced in school textbooks. One is to use the Big Dipper to locate Polaris, and the other is to find Polaris through Cassiopeia.

From the two stars at the end of the Big Dipper's spoon, extend about five times the distance to find Polaris. If the Big Dipper happens to be low in the sky, blocked by houses, you can also refer to the W-shaped constellation Cassiopeia opposite it to find Polaris.

2. Use the starry sky to determine the direction

Like the sun and the moon, the stars also rise in the east and set in the west. Every day the stars start from the same spot and revolve counterclockwise around Polaris.

For example, Orion in winter, when it first appeared in the sky, it was in the east of the sky, and then slowly slid across the sky and fell from the west.

So when you see Orion very close to the horizon, wait a quarter of an hour. If it's going up, it's to the east, and if it's going down, it's to the west.

3. Using the North Star to determine latitude

From the angle of the North Star to us, we can roughly calculate the latitude of the location. It is conceivable that at the North Pole, Polaris is just above our heads.

If we raise our arm to point at Polaris, the angle between the arm and the ground is 90 degrees. As latitude decreases, the angle between our arms and the ground also decreases.

So the angle between the arm and the horizon is roughly the dimension we are in.

4. Test your eyesight, and distinguish colors

Observing the stars was also used to measure eyesight a long time ago. For example, the Arabs in the Middle Ages used the Big Dipper to test people's vision. One of the Big Dipper is harder to see than the other six.

If you can't see clearly for a while, don't worry, just look a little longer, and maybe you will be able to see it.

Many stars are also colored, such as Orion. Orion is the most common constellation in winter, and we have met countless times. The three belted stars in the middle of Orion are best recognized, with two above and below to outline the torso.

The two stars on Orion's shoulder and sword are colored. The star on the left shoulder glows orange, and there is a purple star on the saber below the belt. In fact, that fuzzy point is not a star, but the Orion Nebula visible to the naked eye.