What is the primary use of brightness in determining celestial bodies for navigation?

The primary use of brightness in determining celestial bodies for navigation is to assess their visibility. Brightness helps navigators identify celestial bodies that can be used for navigation, particularly when those bodies are compared against the surrounding sky. A brighter celestial object, such as a star or the moon, is easier to locate and measure, which is crucial for making accurate navigational calculations.

When navigating, visibility is paramount. If a celestial body is too dim, it may not be reliably used for navigation. Therefore, knowing how bright an object appears allows sailors to determine if it can be effectively used for positioning. This characteristic is essential in celestial navigation, as it directly impacts the sailor’s ability to establish their position on the Earth’s surface based on the location of stars and planets.