Captain William Henry Smyth
Oct 12, 1830 No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827
A standard Greenwich star, at the tip of the Little Bear's tail, with a companion in the sp quadrant. A 2½, topaz yellow; B 9½, pale white. A is Polaris, and from its perpetual apparition in this hemisphere, the most practically useful star in the heavens, whether to the astronomer or the seaman; and the want of such a constant reference at the opposite pole is severely felt. Piazzi devoted much labour to obtain all the conditions of this remarkable star, and prudently concluded that, in consequence of the great and inconstant precession in the immediate vicinity of the pole, it is difficult to separate the proper motions in space from that element: it was also narrowly watched for the detection of parallax, from 1802 to 1804, at each season, in January, July, April, and October, and it was deemed that an absolute quantity of 1".31 was fairly deduced. It was first classed double by William Herschel, being his 1, IV.; and the mean of his observations for 1779, 1781, and 1782, give:
Pos. 202°58' Dist. 18".47 Ep. 1781.50But the correction due to precession being necessary from the variation of an angle of position so near the pole, to reduce the observations from one date to another, I followed Hershel's method; and the amount, -2°39', for the forty-nine years between the above epoch and my first measures, brings Hershels's position to 205°37'.
M. Struve made a series of interesting observations on this object from 1814 to 1819, not only to ascertain the proper motion of both components, but also to deduce the annual parallax and the aberration of light, and find whether very small stars give the latter different from the large. But he found so small a quantity for parallax, (-0".32) that if it was not owing to inevitable error of observation, it is at least what it ought to be. [Hipparcos parallax value is 7.45mas] As to aberration, he found a constant of 20".112, indicated by Polaris and its acolyte, and by other stars = 20".300.
H. and S. were the next examiners of this interesting star, and from the result of not fewer than a hundred measures, obtained this general mean:
Pos. 208°49' Dist. 18".70 Ep. 1823.06We may therefore, on the whole, presume that these stars are unchanged. A is marked 2.3 magnitude from the rule I have adopted, otherwise it is not even a very bright third size. It was ranked γ by Ptolemy, and Copernicus adopted it; but Tycho elevated it to the 2nd magnitude; and Kepler who, in the Rudolphine Tables, speaks of it as vulgo Polaris, rates it the same.
[236° 18".4 2016 WDS]
At present it is only 1°32' from the polar point, and by its northerly precession in declination will gradually approach to within 26' 30" of it. This proximity to the actual pole will occur in A.D. 2095, but will not recur for 12,860 years. The period of the revolution of the celestial equinoctial pole about the pole of the ecliptic, is nearly 26,000 years; the north celestial pole therefore will be, about 13,000 years hence, nearly 49° from the present polar star.
The alignment rule for finding this star, is so well known that it scarcely demands repeating: yet it may be as well to remind the reader, that an imaginary line through the two well-known pointers, α and β Ursce Majoris, nearly passes over it; and once found, it will not readily be mistaken, or forgotten, since, to the naked eye, it appears always in the same place.
In the alignment of the heavens, it may assist rough estimations to assume the distance between the Pointers at 5°, and that between the Pointers and Polaris at about 30°, which, though not the true distances, will serve as a gazing scale. Hence the poetaster:
The ever watchful Kokab guards,The use of the Pole-star in navigation is recorded to have been introduced by Thales; but as it was very anciently called Phoenice, and that philosopher also resided in Phoenicia, it was probably derived from the mariners of that nation, and has ever since been the "lode-star" of seamen. Aratus mentions it as a sure sea-guide, or beacon; saying, —in voce Germanici—
while Dubhe points the Pole;
The Pole at rest, sees Heaven's bright host
unwearied round him roll.
Certior est Cynosura tamen sulcantibus æquor.Dryden has happily described the infancy of navigation :
Rude as their ships were navigated then,Among our own seamen, the Stella Maris, or Pole-Star, and its companions, hare immemorially been under requisition. Recorde tells us, in the Castle of Knowledge, nearly 300 years ago, that navigators used two pointers in Ursa,—"which many do call the Shafte, and other do name the Guardas, after the Spanish tonge." Richard Eden, in 1584, published his Arte of Navigation, and therein gave rules for the "starres," among which are special directions for the two called the Guards, in the mouth of the "horne," as the figure was called. See β Ursae Minoris.
No useful compass, or meridian known ;
Coasting they kept the land within their ken,
And knew no north but when the Pole-star shone.
In the Safegard of Saylers, 1619, are detailed rules for finding the hour of the night, by the "guardes:" and the Bears generally were regarded as rustic time-pieces, whence Shakspeare, in the Gadshill affair, makes the carrier exclaim, " An't be not four by the day, I'll be hanged: Charles's wain is over the new chimney, and yet our horse not packed!"
As to the Little Bear, the whole animal is swung round by the tail every twenty-four hours: whence the general name for the pole was Kotb, which means the spindle or pin fixed in the under-stone of a mill, around which the stars typifying the upper stone turn. Hence, also, the Ludentes, or Dancers, of old.
I more than once attempted to fix the place of a little star, called Blucher, by some of the savans, which precession will have now brought within 2' of the pole. But being only of the 10th magnitude it is a difficult object to touch in RA, and there is a wide companion still smaller. A nebula, like a dull star, is perceivable near it, and is H. 250, Polarissima; so called from its proximity to the pole. Insignificant, however, as is this little star with its warlike name, it is as much the pole point of the zodiac, as α Draconis is that of the Ecliptic.
Arctos minor, or the Lesser Bear, is not mentioned by Hesiod or Homer, therefore was probably not yet admitted among the constellations in that shape: indeed, Cynosura was more likely to have been represented by a dog. Jacob Bryant, dreaming of Philistines, considers the word as having been borrowed by the Greeks from Cahen Ourah. Thales is reported to have formed it, from perceiving the seven principal stars make a similar figure to the well-known wain of the Great Bear; but reversed with respect to each other: whence Aratus assures us that both the Bears the magna minorqite feræ of Ovid were called αμαξα, or waggons, by the Greeks. But instead of the obtuse-angled projection of the Great Bear's stern, the Lesser Bear's tail curves gradually till it reaches the Pole-star. It is, however, a perplexing asterism, from the number of hours of RA it extends over, and its components have been thus registered:
Ptolemy . . . 8 stars Hevelius . . . . 12 starsIt appears that Ursa minor was a favourite constellation among the Arabians, who called the pole-star Jedi, or the Kid; and Al Kaukab-al-shemálí, the Northern star, an appellation originally given to β, which in Ptolemy's time was nearer to the pole than α. On the Cufico-Arabic globe, described by Assemani, the asterism is written Al Dubb-al-ashgar: and in the Alphonsine Tables it is corruptly termed Alrucaba which term has been discussed by Grotius, Hyde, and Ideler, as grounded in Hebrew, Chaldaic, or Arabic.
Tycho Brahe . . 20 Flamsteed . . . 24
Kepler . . . . 21 Bode . . . . . 75
We are told that the pole was also termed Al Kiblah, because of the obligation in Mahometan prayer to know which way the head is. To find the kiblah in an unknown place, they looked to Polaris and could thereby readily orientize themselves. To this necessity we are considered to be indebted for the astronomy of the Abbaside Caliphs.
― A Cycle of Celestial Objects Vol II, The Bedford Catalogue, William Henry Smyth, 1844
1 object found within 120'
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