Day movement

The day movement is the movement of the celestial sphere observed in the course of a day. It is a retrograde movement, of a schedule looking south, and of anti -Horary sense looking north, looking to the east and looking west.

Let's take as an example the sun, which comes out for the east and is put in the west, which in the northern hemisphere can be seen as a movement in a schedule, although slightly slower than the distant stars. These move in accordance with a syndéreo time, while the apparent movement of the sun is consistent with solar time.

Even the Copernican revolution, astronomers believed that it was a concrete movement of the stars. From Copernicus we know that it is the Earth that revolves around its axis completing a turn in 23 h 56 min 4 s (a syndéreo day). However, the same Ptolemaic conception continues, assuming that the movement of the celestial sphere is apparent, the earth being the one that really rotates.

located in the horizon plane and in the course of a day, an observer sees the stars turn around the axis of the world, in the east-south-west direction watching the south, or in the main sense- North-West looking north.

The only points of the celestial sphere that remain fixed are the celestial poles; All others, and the stars with them, seem to turn in concentric circles around those. The Celeste North Pole is located on the northern cardinal point at a height that coincides with the latitude of the observer. In the North Pole, an observer would see the polar star in the Zenit. For an observer located in the Earth's Ecuador, the North Pole is on the horizon. To intermediate latitudes, for example at 40º, the celestial pole is at a height of 40º on the horizon.

Among the stars closest to the North Pole, the most easily visible is the Polar Star, which is at a degree of this, and describing a circle around it. The radius of this circle is about twice the angular diameter our moon.

They are called circumpolar stars for a certain latitude those stars that describe a complete circle around the celestial pole without being under the horizon at any time, so they are always visible.

The rest of the stars, including the sun and the planets, describe only part of a circle, cutting the horizon in two points: the ortho and the sunset.

In this daytime movement the stars retain their positions, participating the entire celestial sphere of said movement.

Diurnal movement and astronomical calculations

This apparent movement of the stars in the sky of the observer generates three classic problems in position astronomy, rising and setting, the Maximum digressions of a star and the vertical prime.