True Apparent Places of Thirty-seven of the Principal Fixed Stars for every tenth day of the year. Right Asc. Dec. North. h. m. sec. .2 " Right Asc. Dec. North. h. 18 38 m. sec. Right Asc. h 19 m. sec. Dec. North. 20 Jan. 120 475 5 94 27 51 52 40 36.5 31 45 85 38 50 4 17 48-74 48 65 8 Right Asc. Dec. North. 19 m. sec. " 43 20 77 28 24.0 11 5 03 9.9 648.84 21 5.34 10'6 51.93 64.3 20.83 22.3 32'2 46'15 44.2 48.96 62.9 30.3 46.36 41.4 49.12 61.6 28.7 46'60 38.9 49.30 27.4 46.87 36.9 26.5 47.17 35.3 6 20 93 20.5 21.06 19.0 60°4 21.22 17.6 49'51 59.5 21:41 16.5 49.75 58.9 21.62 15'6 True Apparent Places of Thirty-seven of the Principal Fixed Stars for every tenth day of the year. The Epoch. Upper Culmination at Greenwich. Right Asc. " Jan. 136 1381 44 36-5 14 55-57 56 519 57 57-66 2 73-4 49 13:35 25 407 57 11-18 23 25-3 Dec. South. Right Asc. Dec. South. 79°2 13.25 40.3 11.08 24.1 80'0 31 Right Asc. Dec. North. Dr. Young's Refractions, the Barometer being at 30 inches, and the internal Thermometer at 50, or the external at 47, degrees; with the corrections for + one degree in the thermometer of Fahren one inch in the barometer, and for heit. From page 19 of Vol. 1st of Pearson's Practical Astronomy. 43,8 1,47,088 66 25,9,87,052 78 12,3,41,025 10,2,34,021 9,2,31,018 8,2,27,016 7,1,24,014 6,1,20,012 5,1,17,010 4,1,14,008 3,1,10,006 2,0,07,004 1,0,03,002 0,0,00,000 54 42,21,41,085 67 24,7,83,050 79 11,2,38,023 The correction for an increase of altitude of one inch in the barometer, or for a depression of one degree in the thermometer, is to be added to the tabular refraction; but when the barometer is lower than 30 inches, or the thermometer higher than 47 degrees, the correction becomes subtractive. When great accuracy is required, 0,003 inch should be deducted from the observed height of the barometer, for each degree that the thermometer near it is above 50 degrees, and the same quantity added for an equal depression. Logarithm for converting Sidereal into Mean Solar Time +9.9988126. Mean Solar into Sidereal Time +0.0011874. A second of time, at the Equator, contains 1521 feet. THE UNITED STATES NATIONAL OBSERVATORY AT WASHINGTON. Lieut. M. F. Maury, A. M., Superintendent. THIS institution was founded in 1842, under an act of Congress appropriating a sum of money to erect a Depot for the Charts and Instruments of the Navy of the United States, whence our public vessels might be suitably supplied with the nautical works requisite for their safe navigation. The site of the observatory is a beautiful one, commanding a fine view of Georgetown, Washington, Alexandria, Fort Washington (opposite Mount Vernon), and the Potomac River for several miles above and below the city. It occupies University Square, a plot of ground comprising seventeen acres, in the suburbs of Washington, on the left bank of the Potomac, and about one hundred feet above tide water. This was a reservation made by General Washington for the site of a great university. The observatory, however, is a Naval Institution, conducted entirely by naval officers, under the direction of Lieut. M. F. Maury, A.M., as principal superintendent. The law requires that the superintendent or director shall be either a Lieutenant, Commander, or Captain in the Navy of the United States. The main building is of brick, fifty feet square, and two stories in height, surmounted by a revolving dome of twenty feet diameter in the clear, in which is placed the large equatorial, a splendid instrument, from the manufactory of Merz & Mahler, Munich. Attached to the main building, as observing rooms, are wings extending eighteen feet to the east and west, and a projection of thirty-six feet (in two apartments) to the south. The observatory is furnished with a set of excellent astronomical instruments, consisting, 1, Of the large refractor, in the dome already alluded to, of 14 feet focal length, with an object glass having 9 inches clear aperture; it is equatorially mounted, and furnished with clock work. 2. A transit instrument of 7.1 feet focal length, and 5.3 inches clear aperture; made by Ertel & Son, Munich, and mounted on the meridian in the west wing, where there is also a clock with a mercurial pendulum, made by Parkinson & Frodsham. In the east wing is, 3. a meridian circle, by the same makers; its object glass having 3.8 inches aperture, with a focal distance of 4.9 feet. This instrument is provided with a 30 inch circle, divided into arcs of 3', and read to seconds and tenths by four microscopes. A few feet from this, in the same room, stands, 4. the elegant mural circle, an English instrument, by Troughton & Sims, of 5 feet diameter, divided into arcs of 5' value, and furnished with six reading microscopes, with which subdivisions of the circle are obtained in seconds and parts of seconds. The object glass of the telescope is of the same size with that of the meridian circle, with a focal length of 5 feet; the clock has a mercurial pendulum, and was made by Charles Frodsham. |