Book excerpt: Traditional navigation with a sextant, an almanac, and a book of tables is still thriving, even with the availability of accurate, cheap GPS receivers. Batteries sometimes go dead, and electronic devices fail, especially in salt air. Also, it can be satisfying and fun to work out a position and plot it, all on your own - but getting good at it requires some practice.100 problems is a self-contained book of realistic celestial navigation problems, including excerpts of all the necessary Nautical Almanac pages and sight-reduction tables, with answers and explanations.