These tables were designed for air navigation where weight and space are at a premium, however, they are very popular with sailors due to the fact that at most only three books are needed, and that Vol. 1 offers a speedier way to compute stars. The way the 6 volumes of 229 were combined into this 3 volume set is this: volumes 2 & 3 cover all latitudes, but work only for declinations from 0- to 29- north or south. This covers the sun, moon, planets, and only those stars whose declinations fall into this range. Volume 1 contains some stars (whose declinations may be more than 29-) that are pre-selected for optimum viewing and direction. This volume is applicable for an 8 year period, centered on its Epoch date. The only drawback to this arrangement, is that it is possible that a star may be needed for the mariner that is not one of the pre-selected ones, and whose declination is more than 29- north or south. This star, if observed on a rare occasion through a break in the overcast, could not be computed using the 249 tables. Never the less this remains the most popular tabular system in use. Because of the high prices of the Government editions, they have been reprinted as Commercial Editions at less than half the price. They are photoduplicates sized at 90% of the originals, and soft covered. They are still easy enough to read, but their smaller size of 8.5 x 11 inches is easier to carry and store.