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Conjunctions of the Moon with the Planets and Stars.
10th, ....y in Libra ....... 9 evening.
PHENOMENA PLANETARUM. . Mercury at his greatest elongation on the 1st as a morning star, angle of elongation 24° 19'. Greatest south latitude on the 5th. Ascending node on the 24th. In conjunction with Venus at 5 in the morning of the 26th, difference in declination 21'. Perihelion on the 29th.
Venus in conjunction with 2 w in Taurus on the 7th, difference of latitude 2. Ascending node on the 27th. In conjunction with H in Gemini on the 28th, difference of latitude 13'.
Phases of Venus. The proportions of the light and dark phases of Venus are as follow :June 1st.--Illuminated disc = 11.5786
Dark part = 0.4214 Mars attains his greatest south latitude on the 7th. In perihelion on the 30th.
Hrs. Min. Vesta, 1st day. Right Ascension, 9 23 N. Declin. 21° 2' 9th
............ 9 35 .......... 20 1
..... 9 48 ......... 18 55 25th
.. 10 1 ........ , 17 44
Hrs. Min, Juno, 1st day. Right Ascension, 10 20 N. Declin. 11° 0' ........ 10 28
10 34 17th ....... ...... 10 37
10 2 25th
10 46 . Pallas, 1st
25th Ceres, 1st
...... 2 0 .... 25th ........ ...... 2 10 Jupite: in quadrature at 15 minutes after 2 of the afternoon of the 18th. Eclipses of the Satellites of Jupiter.
FORM OF SATURN'S RING.
Semi-conjugate axis - 3.94
Sphere of the Fixed Stars. Positions of the principal constellations on the 1st day at 11 in the evening.
On the Meridian. Lupus close to the southern horizon, Libra, Serpens, Corona Borealis, Boötes, Draco near the zenith, Ursa Minor, Tarandus, Custos Messium, Camelopardalis, and Perseus on the verge of the northern horizon. Hercules and Ophiuchus are between
the zenith and S. S. E. E. point of the horizon ; between Ophiuchus and the meridian is Scorpio. Aquila and Antinous, E. S. E. Lyra, Vulpecula et Anser, Delphinus, and Equuleus, due east. The head of Draco, Cygnus, and Pegasus, are between the zenith and E. N. E. Andromeda, N. E. Cassiopeia, N.N.E. Ursa Major, the Lynx, Castor and Pollux, N.W., the latter near the horizon. Centaurus, Corvus, Crater, and Sextans in the horizon from the south to the west. Boötes between Virgo and the Zenith, the latter extending over a large portion of the sky in the S. W.
Telescopic Objects. The following telescopic objects will be in favorable positions for observation during the month.
Hercules. In the girdle of Hercules, between two stars of the eighth magnitude, is a nebula round and bright in its centre; between the knee and left leg is another beautiful nebula 5' in diameter, surrounded with great nebulosity; near K is another bright nebula, -each of these is resolvable into stars. In the breast of Hercules is a planetary nebula ; a, the star in the head, is a double star—the large star red, the small of a bluish green color; this is also a variable star; period of variation 604 days. d is a double star, the largest of which is white, the small reddish white. Y, K, P, n, and 70 are also double stars. The most interesting object in this constellation is ļ, which is a binary system, the large star of a beautiful bluish white, and the small of a fine ash color:—these stars revolve about their centre of gravity. On the 18th of July, 1782, the interval between the two stars was one half the diameter
of the smaller one, with a telescopic power of 460. In 1802 Sir Williain Herschel could no longer perceive the small star ; but in a clear night in September of that year, with the same telescopic power as that before used, the apparent disc seemed to be a little lengthened in one direction. With the ten-feet telescope, and a power of 600, it had the appearance of a lengthened, or rather wedge-formed, star; this celebrated astronomer was convinced that not more than three-eighths of the apparent diameter of the small star was wanting to a complete occultation.
O Majestic Night!
COMETARY ASTRONOMY. Mugnitudes of Comets. The apparent magnitudes of comets not only depend on their absolute bulk, but also on their distances from the earth ; some have appeared whose brightness did not exceed that of very minute stars, others have shone forth as stars of the first magnitude. That which appeared in the reign of Nero is described as not inferior in apparent magnitude to the sun. Hevelius observed a comet in 1652, which he describes as not less than the moon, though it was deficient in splendour, having a pale dim light, and a dismal aspect. The comet of 1577 had an apparent diameter of 25' or 26', a magnitude nearly equal to that of the moon when in apogee. The diameter of the head of the comet of 1769 was about a degree, and its nucleus about 4'; that of 1807 bad its envelope 6' in diameter, and the one that appeared in 1811 exceeded that of 1807 in apparent magnitude.
From the apparent angles under which comets are seen, being ascertained, and their distances determined, their true magnitudes are obtained. The
1805 .... 30
1807 .... 538 The second comet of 1811 possessed a nucleus of prodigious size, being no less than 2637 miles in diameter, or one-third of that of the earth. These diameters are the results of very careful measurements in the hands of good observers; which, however, very often vary, as determined by astronomers, who have measured the same body:-thus in the comet of 1811, Herschel computed the diameter to be the amount just stated, namely, 2637 miles ; Schroëter, a celebrated astronomer, differed very widely from this result, and estimated the diameter to be only 570 miles. The great magnitude assigned to some comets, may be accounted for from the coma surrounding the nucleus, being measured instead of the nucleus; this would make a wonderful difference in the results. In this respect, also, comets differ from planets,--the edge of a planetary disc is