Since J W Norie published the first edition of this famous set of mathematical tables in 1803, the book has become - and remained - a bestseller. Despite developments in electronic navigation it remains an essential requirement for anyone learning and practising astro-navigation. Since the last update in 2007, the editor, George Blance, has made many changes - new tables have been included and obsolete ones deleted to conform with changing techniques of navigation, with the aim of improving the accuracy of the calculated position and reducing the tedium of the calculation. The section Seaports of the World has again been extensively updated and restructured with several hundred additional ports. The ports are listed geographically and also indexed alphabetically to aid identification. 2018 edition.