Some history of astronomy ephemeris

Ephemeris (plural: ephemerides) comes from the Greek "ephémeros", which means "daily. Traditionally, an ephemeris was a table providing the daily positions of the Sun, the Moon, the planets, asteroids or comets in the sky. Astronomers would use these tables to find the celestial objects in the sky.

Christipher Columbus carried two almanacs

Almanach perpetuum, by Abraham Zacuto

1498 Ephemerides, by Johannes Müller von Königsberg. better known as Regiomontanus

1504 , the eclipse that saved Columbus

1680 Connaissance De Temps by French Johann Hecker

In 1766 the first "Nautical Almanac and Astronomical Ephemeris" was published by the Astronomer Royal of England containing ephemeris data for the year 1767. Initially the almanacs provided the data required for the method of lunar distances, a technically demanding and mathematically complex method of determining longitude before the invention of accurate clocks for shipboard use. The common availability of precise chronometers on ships beginning in the early 1800s, and the development of methods of "sight reduction" by Sumner, St.-Hilaire and others, provided an easier procedure for navigators to determine their position at sea. The almanacs provided the necessary data for these methods.

Utilizing the predicted position of stars and planets from the nautical almanac to determine his position and being astonished over the precision of the results, Joshua Slocum writes 1896 in his "Sailing around the World alone": ... I realized the mathematical truth of their motions, so well known that astronomers compile tables of their positions through the years and the days, and the minutes of a day, with such precision that one coming along over the sea even five years later may, by their aid, find the standard time of any given meridian on the earth ... .

Today, the computational power of modern computers, not only allows the calculation of planetary ephemeris with high precision, but also the tabulation of planetary positions on an hourly basis (rather than the traditionally daily basis). The hourly based planetary ephemerides are the primary part of today's nautical almanacs.

Reference 

Sail away