2 m. 7 s.: 1 m. 16 s., and therefore by adding this to 6 m. gives 7 m. 163 s. for the equation at the time required. TABLE Of the Equation of Time for every fifth Day. m. 8. Wednesday, Jan. 1st, to the time on the dial add 3 42 LUNAR PHENOMENA. Phases of the Moon. Last Quarter, 4th day, at 10 m. past 4 morning Moon's Passage over the Meridian. The following table shows at what time the Moon will pass the meridian of the Royal Observatory on certain days during this month, when observations may be conveniently made, if the weather prove favourable. For any other meridian a slight reduction is necessary, which depends upon the longitude of the place as well as the Moon's horary motion. TABLE Of the Moon's Passage over the first Meridian. 4th, 47 5 4 in the afternoon 5 6 7 in the evening 6 24th, 15 10 25th, 17 11 On the 26th of this month the Moon will be totally eclipsed, which will be partly visible at Greenwich; the circumstances being as follow, viz. We have already shown that the phases of this beautiful planet are subject to variation, like those of the Moon, and have explained the method by which they are calculated, as well as solved the problem relative to her maximum brilliancy (see T.T for 1819); we shall therefore only give the results of these calculations for the first of each month in the present year. Illuminated part 11.99878 digits January 1st, {Dark part Venus is, therefore, very near the point of her greatest illumination; but our young readers should be reminded that this is by no means that of her greatest brilliancy. On this subject see T. T. for 1819, p. 51. Eclipses of Jupiter's Satellites. From the number of Jupiter's moons or satellites, and the rapidity with which their revolutions are performed, they are frequently eclipsed by passing through his shadow. These bodies, however, are too small for their eclipses to be subject to common observation, and indeed require a good telescope to observe them with accuracy. The young observer should also be at his telescope a little before the eclipse is expected to take place, that he may be able to observe it with all possible steadiness. To assist him in these respects, we shall insert the times of such of the eclipses of the first and second satellites as are visible at Greenwich. Form of Saturn's Ring. 5 evening 1 morning 7 evening 9 11 night 9 For such explanations as are necessary to enable our readers to apprehend the principal circumstances of this singular phenomenon, we must refer to T.T. for 1819. We shall therefore only insert the results for every third month, leaving the calculations as exercises for our astronomical students. Transits and Altitudes of the Planets. For the information of such of our readers as wish to observe the planets in their passage over the meridian, we shall insert the times of their transit for every 6th day, and their altitudes when on the first meridian. The time of passing any other meridian may also be readily found by adding or subtracting that answering to the difference of longitude; and the meridional altitudes will differ very little for any other part of Great Britain. From having the meridional altitude and the latitude of the place of observation, the declination may be obtained by simple subtraction, for it is always equal to the difference between the altitude and the co-latitude of the place. When the altitude is the greater quantity, the declination, in our latitude, is north, but when it is the less, it is south. Example.—The meridional altitude of Mercury, at the Royal Observatory, on the 1st of May, 1823, is 54o 19'; and as the co-latitude is 38° 29', we have 54° 19′-38° 29′ 15° 50' N. for the declination of the planet on that day.-Again, on the 1st of September, 1823, the altitude of Venus, when on the first meridian, is 26° 46′; and consequently her declination at that time will be 38° 29′-26° 46′ = 11° 43' S. Mercury will be in his superior conjunction about 1 in the morning of the 3d; and Saturn will be stationary on the 4th of this month. The Moon will be in conjunction with the bright star a in Scorpio, at 38 m. past 3 in the afternoon of the 8th; and, at the same time, Mercury will be in conjunction with Venus. They will consequently be seen above each other, Mercury being only 65 south of Venus. The Moon will be in conjunction with Venus at 21 m. after 7 in the evening of the 12th; with Mercury at 34 m. past 10 the same night; and with Mars at 43 m. after 6 the next evening. Jupiter will be stationary on the 21st. Mercury will be in conjunction with Mars on the 22d, the former planet being at that time 27 south of the latter. Saturn will also be in quadrature at 45 m. past 7 in the morning of the 24th. Thus the celestial phenomena of this month supply the young astronomer with numerous opportunities of exercising his powers of observation; and, by combining practice with theory, of advancing in his progress up the mount of that sublime science. But while he thus climbs the steep ascent, and surveys that cerulean vault, so gloriously illuminated with celestial radiance, the sensible mind will feel more than ever grateful for that faculty which enables him to enjoy this astonishing spectacle, and Take in, at once, the landscape of the world At a small inlet, which a grain might close, YOUNG. Ought he not, too, on contemplating such a scene, to experience something of the feeling expressed by the same poet, when he exclaims, Who turns his eye on Nature's midnight face The Naturalist's Diary For JANUARY 1823. Thou hast thy beauties: sterner ones, I own, Thou art austere; thy studded mantle, gay As erst Golconda's; and thy pure array B. BARTON. |