Why does the apparent position of a star slightly differ from its actual position when viewed near the horizon?

The apparent position of a star slightly differs from its actual position near the horizon due to atmospheric refraction. When a star is close to the horizon, its light passes through a thicker layer of Earth’s atmosphere, characterized by varying temperature and density. This causes the starlight to undergo increased refraction, bending more sharply than when directly overhead. The atmospheric lensing effect causes the star’s apparent position to be slightly higher in the sky than its actual geometric position. This phenomenon is most noticeable near the horizon, leading to the observed discrepancy between the true and apparent positions of stars.