The daily east to west motion of celestial objects is caused by the Earth s rotation and is known as diurnal motion . Diurnal motion causes the position of objects to change throughout the day. So, whether or not an object is above the horizon depends, in part, on the time of day. But an object above your horizon at a certain time may not be above the horizon at the same time for another observer at a differrent latitude. Hence, an object's visibility depends not only on the time of day but also on the observer's latitude .
Some objects rise directly at the east point, while others rise north or south of east.
It is important to realize that because all diurnal circles are parallel to the celestial equator objects that rise at the east point must set at the west point. Likewise objects that rise in the northeast must set in the northwest, and objects that rise in the southeast must set in the southwest. The time that an object spends above the horizon depends, essentially, on where it rises. The farther north the rising point the longer an object remains above the horizon while the farther south it rises the longer it remains below the horizon. Objects that rise at the east point are above the horizon for 12 hours and below it for 12 hours.