Final answer:
Coastal refraction error, or astronomical refraction, is most pronounced when there is a long distance between the observer and the object being observed, and when the light passes through several layers of different air temperatures near the coastline or over a large body of water.
Step-by-step explanation:
Coastal refraction error, also known as astronomical refraction, is most pronounced when there is a long distance between the observer and the object being observed, and when the light from the object passes through several layers of different air temperatures near the coastline or over a large body of water.
This type of refraction occurs because the temperature of the air decreases as it gets further away from the warm land and over the cooler water, causing the light to bend. As a result, the object appears higher in the sky than it actually is, causing an error in its perceived position.
For example, when observing stars or planets near the horizon from a coastal area, the light from these celestial objects passes through more layers of air near the water, leading to a larger refraction angle and a greater shift in their apparent positions.