What is the best time to conduct morning and evening star sights?

The best time to conduct morning and evening star sights is during civil twilight and nautical twilight. Twilight is the period when the sun is just below the horizon, providing enough light for celestial navigation while still allowing stars to be visible.

Civil twilight occurs when the sun is between 0 and 6 degrees below the horizon, allowing for sufficient natural light while still permitting the visibility of bright stars. Nautical twilight follows, occurring when the sun is between 6 and 12 degrees below the horizon. This stage allows navigators to use stars for navigation without significant interference from the sun's light.

Using these periods for star sights maximizes visibility and accuracy in navigation, making it easier to identify celestial bodies and ensure accurate measurements. The other choices do not offer the optimal lighting conditions needed for effective navigation using stars, which is why they are less favorable for conducting these types of sights.