Navigational stars

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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. [1] 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.[2]

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.

Contents

[edit] Navigational stars

[edit] Key

Column title Description
No. Index number of the star used in the list of selected navigational stars in the nautical almanac[3]
Common name The common (or proper) name of the star used in the nautical almanac and the American Practical Navigator
Magnitude A logarithmic measure of the brightness of an astronomical object
Bayer designation A stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name
SHA Sidereal hour angle (SHA) is one of the coordinates used in the equatorial coordinate system for describing the position of a point on the celestial sphere
Declination The second coordinate used in the equatorial coordinate system
Distance (ly) The distance from Earth to the star measured in light years
Meaning of name A brief explanation of the meaning or origin of the common name for a star by Nathaniel Bowditch[1]
SIMBAD entry A link to an entry in the astronomical database maintained by the Centre de Données astronomiques de Strasbourg (CDS), France

[edit] Navigational stars

No.[3] Common name Magnitude Bayer designation SHA Declination Distance (ly) Meaning of name[1] SIMBAD entry
1 Alpheratz 2.06 α And 358 N 29° 97 the horse's navel Alpheratz
2 Ankaa 2.37 α Phe 354 S 42° 77 coined name Ankaa
3 Schedar 2.25 α Cas 350 N 56° 230 the breast (of Cassiopeia) Schedar
4 Diphda 2.04 β Cet 349 S 18° 96 the second frog (Fomalhaut was once the first) Deneb Kaitos
5 Achernar 0.50 α Eri 336 S 57° 140 end of the river (Eridanus) Achernar
6 Hamal 2.00 α Ari 328 N 23° 66 full-grown lamb Hamal
* [3] Polaris 2.01 var[4] α UMi 319 N 89° 430 the pole (star) Polaris
7 Acamar 3.2 θ Eri 316 S 40° 120 another form of Achernar Acamar
8 Menkar 2.5 α Cet 315 N 04° 220 nose (of the whale) Menkar
9 Mirfak 1.82 α Per 309 N 50° 590 elbow of the Pleiades Mirfak
10 Aldebaran 0.85 var[4] α Tau 291 N 16° 65 follower (of the Pleiades) Aldebaran
11 Rigel 0.12 β Ori 282 S 08° 770 foot (left foot of Orion) Rigel
12 Capella 0.71 α Aur 281 N 46° 42 little she-goat Capella A, Capella B
13 Bellatrix 1.64 γ Ori 279 N 06° 240 female warrior Bellatrix
14 Elnath 1.68 β Tau 279 N 29° 130 one butting with the horns Elnath
15 Alnilam 1.70 ε Ori 276 S 01° 1300 string of pearls Alnilam
16 Betelgeuse 0.58 var[4] α Ori 271 N 07° 430 the arm pit (of Orion) Betelgeuse
17 Canopus −0.72 α Car 264 S 53° 310 city of ancient Egypt Canopus
18 Sirius −1.47 α CMa 259 S 17° 8.6 the scorching one (popularly, the dog star) Sirius
19 Adhara 1.51 ε CMa 256 S 29° 430 the virgin(s) Adara
20 Procyon 0.34 α CMi 245 N 05° 11 before the dog (rising before the dog star, Sirius) Procyon
21 Pollux 1.15 β Gem 244 N 28° 34 Zeus' other twin son (Castor, α Gem, is the first twin) Pollux
22 Avior 2.4 ε1 Car 234 S 59° 630 coined name Avior
23 Suhail 2.23 λ Vel 223 S 43° 570 shortened form of Al Suhail, one Arabic name for Canopus Lambda Velorum
24 Miaplacidus 1.70 β Car 222 S 70° 110 quiet or still waters Miaplacidus
25 Alphard 2.00 α Hya 218 S 09° 180 solitary star of the serpent Alphard
26 Regulus 1.35 α Leo 208 N 12° 77 the prince Regulus
27 Dubhe 1.87 α1 UMa 194 N 62° 120 the bear's back Dubhe
28 Denebola 2.14 β Leo 183 N 15° 36 tail of the lion Denebola
29 Gienah 2.80 γ Cor 176 S 17° 165 right wing of the raven Gienah
30 Acrux 1.40 α1 Cru 174 S 63° 320 coined from Bayer name Acrux A
31 Gacrux 1.63 γ Cru 172 S 57° 88 coined from Bayer name Gacrux
32 Alioth 1.76 ε UMa 167 N 56° 81 another form of Capella Alioth
33 Spica 1.04 α Vir 159 S 11° 260 the ear of corn Spica
34 Alkaid 1.85 η UMa 153 N 49° 100 leader of the daugthers of the bier Alkaid
35 Hadar 0.60 β Cen 149 S 60° 530 leg of the centaur Hadar
36 Menkent 2.06 θ Cen 149 S 36° 61 shoulder of the centaur Menkent
37 Arcturus −0.04 var[4] α Boo 146 N 19° 37 the bear's guard Arcturus
38 Rigil Kentaurus −0.01 α1 Cen 140 S 61° 4.4 foot of the centaur Alpha Centauri
39 Zubenelgenubi 3.28 α Lib 138 S 16° 77 southern claw (of the scorpion) Alpha Librae
40 Kochab 2.08 β UMi 137 N 74° 130 shortened form of "north star" (named when it was that,[5] ca. 1500 BC - AD 300) Kochab
41 Alphecca 2.24 α1 CrB 127 N 27° 75 feeble one (in the crown) Alphecca
42 Antares 1.09 α Sco 113 S 26° 600 rival of Mars (in color) Antares
43 Atria 1.92 α TrA 108 S 69° 420 coined from Bayer name Atria
44 Sabik 2.43 η Oph 103 S 16° 84.1 second winner or conqueror Sabik
45 Shaula 1.62 λ Sco 097 S 37° 700 cocked-up part of the scorpion's tail Shaula
46 Rasalhague 2.10 α Oph 096 N 13° 47 head of the serpent charmer Rasalhague
47 Eltanin 2.23 γ Dra 091 N 51° 150 head of the dragon Eltanin
48 Kaus Australis 1.80 ε Sgr 084 S 34° 140 southern part of the bow (of Sagittarius) Kaus Australis
49 Vega 0.03 α Lyr 081 N 39° 25 the falling eagle or vulture Vega
50 Nunki 2.06 σ Sgr 076 S 26° 220 constellation of the holy city (Eridu) Nunki
51 Altair 0.77 α Aql 063 N 09° 17 flying eagle or vulture Altair
52 Peacock 1.91 α Pav 054 S 57° 180 coined from the English name of Pavo (constellation) Peacock
53 Deneb 1.25 α Cyg 050 N 45° 3200 tail of the hen Deneb
54 Enif 2.40 ε Peg 034 N 10° 670 nose of the horse Enif
55 Al Na'ir 1.74 α Gru 028 S 47° 100 bright one (of the fish's tail) Al Na'ir
56 Fomalhaut 1.16 α PsA 016 S 30° 25 mouth of the southern fish Fomalhaut
57 Markab 2.49 α Peg 014 N 15° 140 saddle (of Pegasus) Markab

[edit] Star 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 - a star chart is helpful in locating these relationships.[6]

Equatorial stars
Equatorial stars[7]

Star charts are based upon the celestial equator system of coordinates, using declination and sidereal hour angle (or right ascension).[6]

[edit] See also

Nautical Portal

[edit] References

General
Specific
  1. ^ a b c Nathaniel Bowditch: The American Practical Navigator, 2002 Bicentennial Ed., Chapter 15 Navigational Astronomy, page 248, Figure 1530a. Navigational stars and the planets
  2. ^ United Kingdom Hydrographic Office: 2008 Nautical Almanace, Commercial Edition, Paradise Cay Publications, ISBN 0-939837-76-5
  3. ^ a b c This list uses the assigned numbers from the nautical almanac, which includes only 57 stars. Polaris, which is part of Nathaniel Bowditch's classic list of navigational stars, is listed in the correct position but without a number.
  4. ^ a b c d The suffix var after the numeric value denotes a Variable star whose magnitude changes over time
  5. ^ see also Changing pole stars
  6. ^ a b Nathaniel Bowditch: The American Practical Navigator, 2002 Bicentennial Ed., Chapter 15 Navigational Astronomy, page 249, Section 1532. Star Charts
  7. ^ Nathaniel Bowditch: The American Practical Navigator, 2002 Bicentennial Ed., Chapter 15 Navigational Astronomy, pages 250-251, Figures 1532a+b.

[edit] External links