The Nautical Almanac and Astronomical Ephemeris Part 1, had become a publication in its own right in 1896 when Downing separated the volume into two. Part I, contained the data that were needed by navigators at sea for the determination of their position, which would be published separately so that seamen would not need to pay for, or carry Part II. While, Part II contained the high-precision data for the use of astronomers. [OED / GAW].
Cowell, for the 1914 edition, the first he was responsible for, retitled Part I to The Nautical Almanac, Abridged for the Use of Seamen.