I agree with David Williams’ suggestion. Celestial Navigation in the GPS Age, by John Karl is an excellent book. But I don’t agree with the idea of beginning on page 77, if I’m interpreting his suggestion correctly. It would be much better to start on page 1. The great virtue of John Karl’s book is that he explains the” why” of celestial navigation, not just the “how”. The “cookbook” approach of just using formulas or equations without an inkling of what you are doing is not very satisfying and may lead to mistakes. By the way, the name of the book is somewhat confusing; GPS does not play a significant role in the text. “Celestial Navigation in the late 20th century” would be a more accurate, if less glamorous, name.