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This occultation will be visible throughout the United States, and will be the most interesting in the year.

Immersion
Emersion

* December 15th. Occultation of pe Ceti.

9h. 40m. 45.6s. A. 0' 31" North of the Centre.

10 56 17.6 2 44 ) South. D's S. D. at Im. 16' 34.7'' ; at Em. 16' 33.9''.

* Deceinber 17th.' Occultation of Aldebaran.

Immersion
Emersion

4h. 53m. 35.4s. A. 0' 6'' North of the Centre.

5 47 25.5 4 19
D's S. D. at Im. 16' 44.0'' ; at Em. 16' 47.1".

}South.

8.

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December 24th. Occultation of the Planet Saturn.

h. m. Contact nearest limbs of D & h 9 57 53.6 M. 1 18.6 Immersion of h's Centre

9 58 9.9 1 18.7 Total Immersion of h

9 58 26.2 1 18.8 | South of the Contact nearest limbs

10 55 31.6 1 55.0 Centre. Emersion of h's Centre

10 55 47.2 1 55.1 Total Emersion

10 56 2.7 1 55.3) D's S. D. at Im. 15' 49.7'' ; at Em. 15' 46.2". h's S. D. 8.55''.

«Appulses of the Moon to Planets and Stars in 1831, at Boston; all, or

nearly all, of which will be Occultations in some part of the United States.

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OCCULTATIONS OF THE PLANETS* AND OF THE STARS REGULUS

AND ALDEBARAN, VISIBLE IN 18:31 IN THE CITY OF CHARLES-
TON, SOUTH CAROLINA, IN MEAN TIME, FOR THE MERIDIAN OF
CHARLESTON.
February 13th.

Occultation of Venus.
Immersion of ¢ Centre Oh. 55ın. 59s. A. 14' 27" South of the Centre
Emersion

1 30
57

15 24 3 of the Moon. D's S. D. at Im. 16' 2.9"; at Em. 16' 3.0" S. D. 4.99".

February 19th. Occultation of Aldebaran. Immersion

10h. 55m. 57.75. A. 3' 39'' North of the Emersion 11 54 50.2

Centre. D's S. D. at Im. 16' 13.9"; at Em. 16' 10.8". * April 15th.

Occultation of Aldebaran. Immersion

9h. 44m. 37.9s. M. 10' 14" North of the Emersion

10 34 58.6

6 21 ) Centre. D's S. D. at Im. 16' 33.7"; at Em. 16' 36.3".

67 3

s.

11

13 33.1)

June 29th. Occultation of Jupiter and his Satellites.

h. m.
Contact nearest limbs D & 4 0 49 53.4 M.
Immersion of H's Centre 0 51 50.2 13 31.4
Total Immersion

0 53 55.8 13 29.5 South of the Contact nearest limbs

1 34 6.7 12 54.0 Centre. Emersion of the Centre

1 36 11 2 12 52.2 Total Emersion

1 38 6.7 12 50.5 D's S. D. at Im. 15' 20.7"; at Em. 15' 22.2". H's S. D. 21.60".

August 30th. Occultation of Aldebaran. Immersion

7h. 51m. 51.1s. M. 10' 28" South of the Emersion

8 51 15.6 10 53 S Centre. D's's. D. at Im. 16' 23.5''; at Em. 16' 20.8".

Immersion
Emersion

October 2dh Occultation of Regulus.

4h. 57m. 53.8s. M. 7' 10" North of the

6 4 44.8 4 2 3 Centre. D's S. D. at Im. 15' 50.1"; at Em. 15' 52.9."

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* It was originally

intended to compute all the occultations of stars, of not less than the fifth magnitude, for Charleston and Washington, as well as for Boston ; but the calculo tion of the eclipse of the 12th of February occupied so much time (five months), that we were compelled to defer carrying our intention into full effect, until another year.

* December 17th. Occultation of Aldebaran. Star rises eclipsed 4h. 14m. Os. A. Emersion

4 56 52.2 7' 42.7". South of the Centre,

D's S. D. at Em. 16' 43.7".

December 24th Occultation of Saturn. Contact nearest limbs D & h 9 39 38.3 M.

53.6 Immersion of the Centre 9 39 57.7

7 53.4 Total Immersion

940 17.0

753.3 South of the Contact nearest limbs

10 31 44.6

7 50.6 Centre. Emersion of the Centre

10 32 2.8

7 50.7 Total Emersion

10 32 21.0 7,50.8
D's S. D. at Im. 15' 50.7"; at Em. 15' 47.2'. h's S. D. 8.55".

h. m.

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APPULSES OF THE MOON TO THE PLANETS AND THE PRINCIPAL

FIXED STARS, AT CHARLESTON, IN 1831. *January 23. Nearest Ap. ) to a 8 at 3h. lm. A. * 2' 10" North. July 12.

q 요 6 2

f 10 October 29.

a d2 7 15 M. * 7 15

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The importance of large eclipses of the Sun and of occultations of stars and planets by the Moon, for the determination of terrestrial longitude (the latitude being always easily ascertained), has long been known. When thus carefully determined, it will be as near to the truth as when deduced from a very large number of lunar distances, or of transits of the Moon and a star; but where the tables of the Moon are relied on, the longitude, even thus obtained, is still somewhat uncertain, on account of the small error which is sometimes found in them; if, however, it is deduced from a corresponding observation of the same eclipse or occultation made in one of the observatories of Europe, or in any other place, of which geographical position is well determined, it will be free from this as well as other sources of error, if the observations are correctly made in both places.

On another account, the subject of occultations has at all times been an interesting and important one, both to the practical and theoretical astronomer; viz. they frequently present some remarkable phenomena with respect to light, when the edge of the Moon comes in contact with the star, the star sometimes appearing to be projected on the disc of the Moon. This circumstance has lately been very particularly attended to, and numerous instances are given by members of the Astronomical Society of London, who suppose that this appearance is more frequent (or at least more frequently recorded) as to Aldebaran, than as to any other star, accompanied, however, with anomalies, for which it is difficult to account.

It is therefore hoped that our astronomers will be induced to look out for the occultations of this star, not only with a view to ascertain the longitude of the place of observation, but to determine whether it does not appear projected on the face of the Moon; in doing this, particular attention should be paid to the fo.lowing circumstances.

* See a paper read before the Astronomical Society of London, by Mr. South, their President, in the transactions of that Society in 1829; also remarks on the anomalies ob served in the occultations of Aldobaran of August 21st, October 15th, and December 9th, same year.

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1. Whether the star undergoes any change of light, of color, or of motion, on its immediate approach to the edge of the Moon.

2. Whether it appears to be projected on the Moon's disc, and if so, for how long a time.

3. Whether the dark limb of the Moon be distinctly visible, and well defined, at the time of the phenomenon.

4. Whether the 'star, on its emersion, appears on the Moon's disc, or emerges quite clear of the Moon's border.

Between August 1829 and July 1830 six occultations of this star were observed in Boston, and in each of them, when the Immersion or Emersion took place on the dark side of the Moon, it appeared to be instantaneous, and when on the enlightened side, the star usually became so tremulous, near the Moon's edge, as to cause an uncertainty of one or two seconds in the time of its taking place; but in two instances, viz. on the 28th of March last and 16th of July, the star did actually appear projected for the space of between one and two seconds on the lunar disc, or as if about to pass between the Moon and the Earth; its red color remained unchanged, but its light was very much more brilliant than usual.

It will be noticed, that the occultations of the planets and of the stars a 8 and a d (excepting that of a 8 on the 9th of June, or day of new Moon) which take place whilst the Sun is above the horizon, only have been computed; the occultations of the other stars have been neglected, as they will be rendered invisible by the light of the Sun.

In the computation of the occultations last year, the diameter of the Moon was reduced four seconds for inflexion, according to the theory of Duséjour; this year, this reduction has been altogether neglected.

The elements of the eclipses, in the Appendix, are given for mean solar time of the meridian of Greenwich, and of the occultations in mean solar of that of Berlin, which is Oh. 53m. 33.6s. East of Greenwich, or 6h. lm. 15.6s. East of Washington. When it is desired to convert mean into apparent time, the equation, in these elements, must be applied with the sign prefixed to it; but when apparent is to be converted into mean, the sign must be reversed.

No sign is prefixed to the hourly motion of the Moon in Longitude, of the Sun in Longitude or Right Ascension (A. R.), or of Sidereal time, as it is always to

For the accurate calculation of the time of the phases of a solar eclipse or occultation, at any place, the latitude of the place, and the equatorial parallax of the Moon, must be diminished for the ellipticity, or flattening at the poles, of the Earth; which, though not precisely determined, is generally supposed to be about one three-hundredth ; the reductions for this quantity will be found in the 38th table of the sixth stereotype edition of the “New American Practical Navigator," or they may be computed by the following formule.

Let L be the latitude and R the reduction to the geocentric latitude, then log. cotang. (L-R)= 0,0029001 + log. cotang. L.

The reduction of equatorial parallax (57' for example) may be found thus, 5.7'' -5.7" cos. 2 L.

The reduction of the latitude is nothing at the Equator and the Poles, and greatest in latitude 45°, where it is – 11' 28.7".

The reduction of the parallax is also nothing at the Equator, but greatest at the Poles, where it is one three-hundredth of the whole parallax; in Lat. 45° it is half that quantity.

The elements of the eclipses, with the exception of that of February 12th, and of the occultations, with the exception of the places the stars, were computed from the Berlin Astronomisches Jahrbuch (Astronomical Year

86

ECLIPSES OF THE SATELLITES OF JUPITER.

Book) for 1831, edited by the celebrated Encke, a work far superior, both as to matter and arrangement, to any thing of the kind hitherto published.

The places of all the stars, but « 8 and a 2, were computed from Mr. Baily's Catalogue of Zodaical Stars, which was taken from the Catalogue recently published by the Astronomical Society of London, and were also carefully compared with their places in the Catalogue in the Appendix to the first volume of Dr. Pearson's Practical Astronomy. The longitude and latitude of Aldebaran and Regulus are the mean of the determinations at the astronomical observatories of Greenwich and Konigsberg.

Prof. Bessel's determination of the Obliquity of the Ecliptic, and the correction of the mean place of the Sun and Stars for the Aberration of Light and Nutation of the Earth's axis, have been invariably used.

The aberration of the planets was calculated by the formulæ in Vol. III, p. 106, of Delambre's Astronomy.

ECLIPSES OF THE SATELLITES OF JUPITER IN 1831, Visible throughout, or in some part of, the United States; the Phases

of which are expressed in Mean Solar Time for the Meridian of Washington, reckoned according to the manner of Astronomers; who begin the Day at the Noon of the Civil Day, and count the Hours up to 24, or to the succeeding Noon, when another Day is commenced.

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Sat.

d. 1 May 26 2

29 4

31 1 June 5 3

5 1

7 2

12
3

13
1
2

20
1

23 1

27 1

30 2

July 2 1

7 3

8 3

9 2

11 1

15 3

16 1

18 4

18 4

22 1

23 2

24

25 4

25 2 Aug. 1 1

3

h. m.
17 33 47
18 11 51
17 50 19
15 49 42
16 1 7
17 43 19
15 22 1
16 28 43
14 5 19
17 58 45
15 58 53
17 52 23
14 14 16
15 5 39
16 7 46
12 25 50
15 58 48

41 55
18 16
16 24 51
12 29 40
13 52 11
18 25 15
14 23 13
12 11 46
16 16 47
12 33 18
14 47 19
18 10 24
12 38 47

18 23 23

30 April 6

15 17 22 23 23 24 29

30 May 1

1 1 8 12 15 18 19 22 24

h. m.
17 22 43
11 56 59
14 32 27
12 22 49
15 56 33
16 26 13
16 22 14
11 50 34
12 48 34
14 25 37
14 42 31
17 0 35
16 36 35
11 5 5
14 18 12

8 52 58
12 59 19
11 56 4
11 27 46
14 53 40
12 22 54
15 56 53
14 2 35
16 48 10
13 9 13
11 16 50
16 23 12
13 11 31

7 40 10 15 6 19

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