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'''Navigation''' is the process by which a ship (or other vehicle) gets from one place to another. The process requires planning, recording, and controlling the movement of the ship. An essential attribute is being able to calculate one's position. This requires a variety of increasing sophisticated techniques, including [[dead reckoning]], [[piloting]], and [[celestial navigation]]. (Modern navigation is based on positions established by electronic data from satellites.)

By the time that we join Jack Aubrey on the [[Surprise]] in 18** , most of the tools and techniques for successful navigation were developed, particularly where the fleets of the period operated. The compass provided general direction for travel and wind although magnetic variation as the cause of inaccuracy was not fully understood. Charts, in large measure were more or less reliable and becoming more detailed as navies rushed to produce detailed records of their new territories. Distance was measured by log whose margin of error for dead reckoning was insignificant in relation to the stately ship speeds.  [[Latitude]] as a measure and device was solved, and its increasing precision was the product of better tools culminating in the [[sextant]], in its more or less final form in about 1730.  The [[Nautical almanac]] first published in 1767 provided the data to facilitate celestial navigation. The position of  [[Longitude]], had long been problematic and resolved only by the most complex of complications comparing the position of the moon relative to stars, known as lunars. Longitude too was finally solved with Harrison's chronometer as established by Cook's circumnavigation of 1779. Readily available accurate time pieces solved longitude. 

Nonetheless the knowledge, its skillful application and the tools were variously available to ships though out the period. In addition long periods of bad weather could make precise celestial navigation impossible leaving the ultimate safety of the ship to dead reckoning and seamanship.  All mariners were most conscious of the potential dangers, particularly when closing with land.  All British sailors would have known the fate of Sir Cloudesley Shovell's fleet which he drove onto the rocks of the Scilly isles by mis-judging his actual position.

Patrick O'Brien reflects these concerns and realities in the novels of the Aubryiad. Jack Aubrey's navigational concerns are indicative of his role and responsibilities and are one aspect that provides the novels historical texture and content. Patrick  O'Brian as a creative author also uses these concerns to develop characters, plot, context and lyricism. To paraphrase Freud, sometimes [[Saturn]] is just Saturn, and a means to provide navigational context; at other times O'Brian's celestial bodies are much much more.