There are two main reasons why stars appear to move in the night sky:

• Earth's rotation: As the Earth rotates on its axis once every 24 hours, the stars appear to move from east to west in arcs across the sky. This is because the Earth is literally carrying us beneath the stars, making it appear as if they are circling around us.
• Earth's orbit around the Sun: As the Earth orbits the Sun, different constellations become visible at different times of the year. This is because the Earth's position in its orbit changes the angle from which we view the stars. For example, the constellation Orion is visible in the winter sky, while the constellation Sagittarius is visible in the summer sky.

In addition to these two main reasons, there are a few other factors that can affect the apparent movement of stars:

• Proper motion: Stars are actually moving through space, but their motion is so slow that it is not visible to the naked eye. However, over long periods of time, the proper motion of stars can cause their positions in the sky to change.
• Parallax: Parallax is the apparent displacement of an object due to a change in the observer's point of view. When viewed from different positions on Earth's orbit, nearby stars appear to shift slightly against the background of more distant stars. This effect is called parallax, and it is used to measure the distances to nearby stars.

The reasons why we can see some stars all year round and others only at certain times of the year have been explained above. In summary, it is due to the combination of Earth's rotation, Earth's orbit around the Sun, and the proper motion of stars.

Dr Yasith Ramawickrama thank you for your contribution to the discussion

As Earth spins on its axis, we, as Earth-bound observers, spin past this background of distant stars. As Earth spins, the stars appear to move across our night sky from east to west, for the same reason that our Sun appears to “rise” in the east and “set” in the west. This motion is due to the Earth's rotation. As the spin of the Earth carries us eastward at almost one thousand miles per hour, we see stars rising in the East, passing overhead, and setting in the West. The Sun, Moon, and planets appear to move across the sky much like the stars. As the Earth rotates with an axis that is pointed in the direction of the North Star, stars appear to move from east to west in the sky. Stars and constellations stay in approximately the same spot for many, many years. They only appear to move in the sky during the year because we are on a moving planet. Because the constellations are in a fixed location, they are often used as landmarks in the sky. Those slow relative changes in position give each star in our sky a particular "proper motion" a change in angular position. The proper motion of most stars is extremely small, measured in milli-arcseconds per year, where an arcsecond is 1/3600 of a degree, and of course milli means a thousandth of that. That's because the Earth's axis points at a point in the sky around which everything appears to move, including the stars. In the North, this happens to be very close to a star called Polaris, or the North Star. It is in the constellation called Ursa Minor, or the Little Bear. The constellations you can see at night depend on the time of year. Earth orbits around the Sun once each year. Our view into space through the night sky changes as we orbit. So, the night sky looks slightly different each night because Earth is in a different spot in its orbit. These apparent star tracks are in fact not due to the stars moving, but to the rotational motion of the Earth. As the Earth rotates with an axis that is pointed in the direction of the North Star, stars appear to move from east to west in the sky. Not only does the earth rotate, but it also Orbits around the Sun. Where the Earth is located in its yearly orbit determines its seasonal constellations, because our perspective of the sky has changed. The appearance of the sky rotating is actually caused by the rotation of the Earth.