The simplest version of this sextant got me across the Atlantic, accurate landfall and all. Three models varying in features and cost. Top of the line has a full-horizon Beam Converger mirror and LED lighting.
Here is the training, in detailed list form, needed to complete the US Sailing course on Celestial Navigation. The organization also publishes manuals for these skills.
Professional and yachting sextants and accessories, including telescopes, artificial horizons, prisms and lenses.
The chapter on the sextant from the 1995 edition of The American Practical Navigator, originally published in 1802 and updated by NIMA. 10 pages with diagrams and examples.
The chapter on "the sailings" from the 1995 edition of The American Practical Navigator, originally published in 1802 and updated by NIMA. 17 pages, with diagrams and examples, on finding the course and distance from one point to another.