[2][3] Except at the geographic poles, any celestial object passing through the meridian has an upper culmination, when it reaches its highest point (the moment when it is nearest to the zenith), and nearly twelve hours later, is followed by a lower culmination, when it reaches its lowest point (nearest to the nadir).
Three cases are dependent on the observer's latitude (L) and the declination (δ) of the celestial object:[citation needed] The third case applies for objects in a part of the full sky equal to the cosine of the latitude (at the equator it applies for all objects, because the sky turns around the horizontal north–south line; at the poles it applies for none, because the sky turns around the vertical line).
Stellar parallax appears to be a similar motion like all these apparent movements, but has only from non-averaged sidereal day to sidereal day a slight effect, returning to its original apparent position, completing a cycle every orbit, with a slight additional lasting change to the position due to the precessions.
From most of the Northern Hemisphere, Polaris (the North Star) and the other stars of the constellation Ursa Minor circles counterclockwise around the north celestial pole and remain visible at both culminations (as long as the sky is clear and dark enough).
[9] Any astronomical objects that always remain above the local horizon, as viewed from the observer's latitude, are described as circumpolar.