Astro-navigation from Square One to Ocean-master begins at the very beginning of this relatively complex subject and progresses logically through all the required "astro skills." Each new concept builds on UNDERSTANDING with no learning by rote. A 130-word glossary, 160 diagrams and 40 worked examples, all using 2011 Sun, Moon, planet and star data, are contained in 308 pages. The parts relevant to the RYA Yachtmaster Ocean syllabus are identified. In nine sections, the book begins with the basic concepts of great circles, Greenwich Hour Angle and Declination, describing a heavenly body's position on the celestial sphere which, with the observer's zenith, a body's geographical position and a measured altitude of that body, produces a unique position circle. Greenwich Mean Time and its link to longitude and then latitude estimation from the Sun's meridian passage are explored.