 Culmination, in observational astronomy, the culmination of a celestial object the sun, the moon, a planet, the star, or a deep sky object or constellation is either of two moments when it reaches the observer's meridian on the celestial sphere, on which it appears to move along the circular path over. The course of a day, due to Earth rotation. As viewed from the surface of a tristral body, except its geographic poles, a celestial object passes through the meridian twice a day, once at its upper culmination, when it reaches its highest point is viewed from a given location on Earth, and once at its lower culmination, when it reaches its lowest point. The term culmination is often used to mean upper culmination.