Question 1777Navigation General

The correct answer is D) Errors due to unusual refraction may exist. The reason this is the correct answer is that at low altitudes, the sun's rays pass through more of the earth's atmosphere near the horizon, which can cause unusual refraction effects. This refraction can introduce errors in the observed altitude of the sun, making low altitude sun sights less reliable than higher altitude sights. The other answer choices, while potentially relevant, do not directly address the issue of refraction at low altitudes, which is the primary reason low altitude sun sights are generally not recommended for navigation.