This richly illustrated book covers the history of celestial navigation instruments and describes and illustrates each of the major instrument designs starting with the simplest quadrants and astrolabes, through the cross staff and back staff of the fifteenth and sixteenth centuries, to the invention and improvements that lead up to today’s octants and sextants. A major theme of the story is a presentation of many design improvements that were tried but which ultimately did not succeed. A unique feature of the book is a description of how the instruments were used in practice.

Later chapters deal in detail with the design challenges and the solutions that were tried to produce improvements to each of the major elements of the instruments: the form and structure of the frames; the scales, verniers and micrometers; and the mirrors, prisms, filters and telescopes of the optical system.  One chapter describes the many designs for artificial horizons that were used when the natural horizon was not available - in the fog, on land and in the air. An important and unique chapter deals with the development of celestial navigation instruments for aviation, starting with the early balloonists and ending with the Gemini space flights. A glossary of technical terms and an Appendix on patent literature complete the works.