of the astronomer, which have been devoted indirectly in promoting the security and welfare of his fellow men, while traversing the vast Pacific and rolling Atlantic Oceans: these can best understand and confirm the importance of celestial observations, when for days and nights the skies have been as a desert; no sun, or moon, or stars; above them the scowling clouds, beneath them the rolling waves; the tempest and currents acting in different directions, so as to render unavailing every attempt to determine the situation of the ship; the fears of the stoutest heart are excited, in apprehension of the hidden rock and fatal reef; but if amidst this dreary scene the clouds should break away and discover the blue vault of heaven, and the pale queen of night with her silvery orb, either in conjunction with, or more or less remote from, some well known star that may have befriended many a mariner, then instantly every youthful as well as experienced hand is plying the sextant, and the ship's place is determined by the aid of these luminaries, and the skill of the practical astronomer, on whose observations are grounded those Tables, which are the seaman's most invaluable guide. Having thus briefly glanced at the utility as well as grandeur of the sublime science of astronomy, we proceed to lay before our readers the celestial phenomena for the current year. Obliquity of the Ecliptic. This obliquity has been an interesting subject of investigation from the earliest study of astronomy to the present time: the first observation recorded, that can be depended on, is by Eratosthenes, 230 years before the Christian era; he determined the angle which the Sun's path makes with the equinoctial to be 23° 51' 20"; by a comparison of a hundred and sixty observations since, it is found that this angle is diminishing 51" in a century; the physical cause of this diminution, is the united action of the Sun and planets on the protuberant matter of the Earth's equatoreal regions. There is a remarkable unexplained circumstance attending this phenomenon, namely, that the winter solstice has a less obliquity than the summer solstice, which is supposed to have some connection with a hitherto undiscovered modification of refraction. The following is the measure of the obliquity for the usual epochs during the present year : January.. 1st the true obliquity is 23° 27′ April 1st..... July 1st. October 1st. December 31st 32". 6 January.. 1st the mean obliquity is 23 27 42.5 The equations of the equinoctial points at the same time are as follow; namely, The Sun enters Aquarius at 41 minutes past 11 in the morning of the 20th of this month. He also rises and sets at the following times, which are calculated for Greenwich, but may easily be reduced to any other meridian east or west of the Royal Observatory, by converting the difference of longitude into time, at the rate of 15° to an hour, 15' to a minute, 15" to a second, and either adding or subtracting the result, as the place is east or west of the first meridian. Table of the Sun's rising and setting for every fifth day. Jan. 1st, Sun rises 5 min. after 8, sets 55 min. after 3 The following Table shows what must be added to the solar time, as indicated by a good sun-dial, to obtain the mean time, or that which should be shown by a well-regulated clock at the same moment. The addition for the intermediate epoch is to be found by proportion. Table of the Equation of Time for every fifth day. m. S. Friday, Jan. 1st, to the time by the dial add 3 50 Wednesday, Monday, 6th,. 11th,. .... 6 7 LUNAR PHENOMENA. Phases of the Moon. First Quarter, 2nd day, 34 min. after 2 morning. Full Moon, 9th Last Quarter, 17th New Moon, 24th First Quarter, 31st 47 3 4. 4 afternoon. .10 ....... morning. Moon's Passage over the Meridian. The numbers in the following Table, indicate the times at which the Moon's centre will pass the meridian of the Royal Observatory; for any other meridian a slight reduction is necessary, which depends on the Moon's horary motion, and the longitude of the place. Table of the Moon's Passage over the First Meridian. January, 1st day, 37 m. after 5 in the evening. Venus is the evening star, and passing through the zodiacal constellation Aquarius: this beautiful planet is increasing in brightness and breadth, and having passed her greatest elongation, is rapidly assuming the form of a crescent; the following are the proportional phases: January 1st.-Illuminated part = 5.6586 Eclipses of the Satellites of Jupiter. Jupiter is too near the Sun to admit of any of these eclipses being visible. Form of Saturn's Ring. Saturn is entering the constellation Leo, and advancing to a favorable position for observation. The following are the proportions of the Ring: January 1st.-Transverse axis = 1.000 Conjugate axis = −0.267 Mercury in conjunction with Uranus at 6 in the evening of the 13th of this month. Uranus in conjunction with the Sun at 7 in the evening of the 26th. Mercury will be at his greatest elongation the 27th day, when, should the atmosphere prove favorable, an opportunity will occur, one or two evenings previous, and succeeding, of viewing this planet without the aid of instruments. The other planets of the system are constantly presenting themselves for observation, with the exception of a short space of time about the period of their conjunction; but this messenger of the gods but just appears, as if in haste to discharge his commission, and returns again to lose himself in the solar beams. The author of "The Seasons" beautifully refers to this circumstance in his address to the Sun: Great source of day! best image here below From world to world, the vital ocean round, Soul of surrounding worlds! 'Tis by thy secret, strong attractive force, As with a chain indissolubly bound, Thy system rolls entire, From far "Uranus," wheeling wide his round Of eighty years, to Mercury, whose disc Can scarce be caught by philosophic eye, Lost in the near effulgence of thy blaze." * We restrict the conjunctions to those stars which are likely to be occulted by the moon. |