Navigational stars

The navigational stars are used in celestial navigation because they are some of the brightest celesital objects due to their high luminosities and/or their proximity to our solar system. Most of these stars are a subset of the list of brightest stars and are defined by convention and nautical tradition.

One of the most prominent books on maritime navigation, Nathaniel Bowditch's American Practical Navigator, was the first to list these navigational stars in 1802, and they are still included in the 2002 bicentennial edition of the same book.Nathaniel Bowditch: The American Practical Navigator, 2002 Bicentennial Ed., Chapter 15 Navigational Astronomy, page 248, Figure 1530a. Navigational stars and the planets] They are commonly listed on a page in the nautical almanac to aid navigators, typically on a tear-sheet that then serves as a bookmark throughout the year and is placed on the almanac page for the current three-day period. [United Kingdom Hydrographic Office: 2008 Nautical Almanace, Commercial Edition, Paradise Cay Publications, ISBN 0-939837-76-5]

The coordinates of the stars are typically provided in the equatorial coordinate system, using declination and sidereal hour angle (SHA). By convention, these stars are numbered and listed from west to east, i.e. by descending SHA. The nautical almanac lists 57 navigational stars, whereas the American Practical Navigator lists 58, with the inclusion of Polaris. The nautical almanac typically provides declination only to the nearest full degree in this list, since that is typically sufficient for locating the star with a sextant.

Navigational stars

Key

Navigational stars

tar charts

Star charts provide an aid to the navigator in locating the navigational stars among the constellations. It is useful to be able to identify stars by relative position - astar chart is helpful in locating these relationships.Nathaniel Bowditch: The American Practical Navigator, 2002 Bicentennial Ed., Chapter 15 Navigational Astronomy, page 249, Section 1532. Star Charts] Star charts are based upon the celestial equator system of coordinates, using declination and sidereal hour angle (or right ascension).

ee also

*Celestial navigation
*Nautical almanac
*Sextant
*American Practical Navigator
*Star
**Lists of stars
**List of brightest stars
**List of nearest stars
**List of most luminous stars

References

;General
*Nathaniel Bowditch: The American Practical Navigator, 2002 Bicentennial Ed., Chapter 15 Navigational Astronomy
*List of brightest stars;Specific

External links

* [http://aa.usno.navy.mil/data/docs/Nav_Star_Chart.php Navigational Star Chart]
* [http://www.fourmilab.ch/yoursky/catalogues/navstars.html Object Catalogue: Navigation Stars]
* [http://www.angelfire.com/nt/navtrig/F1.html Index of Selected Stars]