What is the primary publication that provides essential ephemeral data to solve the celestial triangle?

The Nautical Almanac serves as the primary publication offering crucial ephemeral data necessary for solving the celestial triangle. This almanac contains various astronomical data such as the positions of celestial bodies, including the sun, moon, and stars, on a daily basis throughout the year. Navigators utilize this information to determine their position on the Earth's surface by referencing the altitude of celestial bodies observed from their vessel.

The celestial triangle involves using angles measured from the horizon to celestial bodies while also incorporating the geographical position of those bodies, all of which rely on the precise data presented in the Nautical Almanac. Accurate computations from this publication enable navigators to effectively carry out sight reductions, leading to improved navigation accuracy.

Other publications like Sight Reduction Tables, while useful for specific calculations, do not provide the comprehensive astronomical data needed for the celestial triangle on their own. Marine Weather Guides focus on climatic conditions rather than celestial navigation, and Coast Pilot publications present local navigational conditions and hazards rather than celestial data. Therefore, the Nautical Almanac is essential for celestial navigation, making it the correct choice.