Question 1780Navigation General

The correct answer is A) civil twilight. During civil twilight, the sun is between 0 and 6 degrees below the horizon, resulting in the darkest period of the night when stars and planets are most easily observed. This period provides the optimal lighting conditions for observing celestial bodies, as the sky is dark enough to see them clearly, but still receives some residual light from the sun. The other options are incorrect because: B) sunset is too early in the evening for optimal star/planet viewing, C) astronomical twilight (sun 12-18 degrees below horizon) is too dark, and D) nautical twilight (sun 6-12 degrees below horizon) is not as dark as civil twilight for the best celestial observations.