This volume focuses on coastal and ocean navigation with an emphasis on celestial navigation techniques as a back up in the event digital technologies fail. It deals with the main themes and principles of celestial navigation (including time). It covers the syllabus for deck officers working towards the Officer of the Watch (OOW) certificate of competence (COC) awarded by the Maritime and Coastguard Agency (MCA), and for Royal Navy navigation officers working towards achieving the equivalent Navigational Watch Certificate (NWC). The NWC is equivalent to the certificate awarded by the MCA to OOWs in the Merchant Service under the international Standardisation of Training, Certification and Watchkeeping (STCW) agreements. The detailed theory of celestial navigation is provided.