THE NAUTICAL ALMANAC AND ASTRONOMICAL EPHEMERIS FOR THE YEAR 1824. PUBLISHED BY ORDER OF THE COMMISSIONERS OF LONGITUDE. London: PRINTED BY T. BENSLEY, 4, CRANE COURT, FLEET STREET, PRINTER; AND SOLD BY JOHN MURRAY, ALBEMARLE STREET, BOOKSELLER TO THE COMMISSIONERS. 1821. [Price Five Shillings.] ADVERTISEMENT. In continuing the annual publication of the Nautical Almanac, the BOARD of LONGITUDE has been more anxious to attain the highest possible degree of accuracy in the execution of those computations, which have hitherto been considered as requisite for the purposes of navigation, than to add very materially to their number or extent. It has, however, been thought proper to annex to the Almanac a correct Table of Refractions, a Table of Second Differences, and the true or apparent Places of Twenty Four Principal Fixed Stars, for every ten days of the year, corrected for precession, aberration, and nutation. The Table of Refractions is computed by a very simple formula, derived originally from theory, and adapted to the results of the most accurate observations, which have been found to justify the slight deviation from the French Tables, that it exhibits in the mean value of the refraction. The barometrical and thermometrical corrections are a little more at variance with the common mode of computation, and they approach in some degree, for the lower altitudes, to the rules which Bradley had inferred from observation alone. The places of the stars have been principally calculated from Dr. MASKELYNE'S Tables; a second table has been added, for facilitating the extension of a similar computation to some others of the most useful stars. The Tables of the Planetary Motions, which have been employed, are chiefly those which are printed in the third volume of Professor VINCE's Astronomy, with the omission only of some equations which do not materially affect the results: the place of the Moon has been calculated, since the beginning of 1821, from BURCKHARDT's Tables, which are, of a later date; and the Eclipses of Jupiter's Satellites from DELAMBRE's new Tables. For the configurations, HALLEY'S Tables have been hitherto employed: and they appear, with proper corrections of the epochs, to be sufficiently accurate for the purpose. The obliquity of the Ecliptic has been corrected, from the Observations of the Astronomer Royal, since the beginning of 1822. The Moon's Right Ascension and Declination are computed to seconds, for the more convenient observation of the Moon's place on shore, and for the calculation of occultations and many other purposes. At the suggestion of a very distinguished practical navigator, the differences of the Sun's Declination from day to day have been added, for the convenience of seamen. Whether any advantage would be gained from the insertion of the Moon's distance from Jupiter, must depend on the precision of the tables of that planet; a point which is expected to be very shortly determined from the most accurate observations. The attention of the BOARD has been particularly directed to the determination of the conditions, under which rewards are to be proposed for the improvement of Astronomical Tables and of Timekeepers; but all who are acquainted with the present state of this department of science must be aware, that a considerable time will be required, before it will be practicable to ascertain, with sufficient precision, how much has actually been effected, and how much is still required, with respect to both these objects. In the mean time it must be remembered, that the BOARD possesses ample powers to reward any improvement, which they may judge sufficiently important, either in the theory or in the practice of any part of Navigation or Nautical Astronomy. As far, however, as the existing Tables of the Sun and Moon have been examined, they appear to be sufficiently EXTRACT FROM DR. MASKELYNE'S PREFACE. "MAYER'S last Manuscript Tables of the Sun and Moon, and his curious and elaborate Theory of the Moon, were received by the Board of Longitude, after his decease, for which his Widow received a Reward of Three Thousand Pounds, by Act of Parliament; and the celebrated Mr. LEONARD EULER the Sum of Three Hundred Pounds, for having furnished the Theorems made Use of by Mr. MAYER in his Theory. Both the Tables and Theory were printed under my Inspection, and published in 1770. "MAYER'S Tables of the Sun were used in the Computations of the NAUTICAL ALMANAC, from its first beginning in 1767 to that of 1804, inclusive. From the NAUTICAL ALMANAC of 1767 to that of 1776, both inclusive, or the first ten Years, MAYER'S Lunar Tables were made use of. But from the NAUTICAL ALMANAC of 1777 to that of 1788, both inclusive, or the next twelve Years, the Moon's Place was inserted as calculated from new Tables, improved from MAYER'S Tables, composed by the late Mr. CHARLES MASON, under my direction, from Calculations made by Order of the Board of Longitude upon the Series of Lunar Observations made by the late Dr. BRADLEY, and published in the NAUTICAL ALMANAC of 1774; in which new Tables the Epoch of the Moon's mean Longgitude is 1" less, that of the Apogee is 56" less, and that of the ascending Node 45" more than in MAYER'S printed Tables, and the Equations are calculated to tenths of a second; and moreover one new Equation is introduced, whose argument is the mean Distance of the Moon from the Sun's Apogee, and maximum is 16". 4. But from the NAUTICAL ALMANAC of 1789 to that of 1804, both inclusive, the Moon's Place was inserted as calculated from new Tables still further corrected by Mr. MASON, entitled by him, TABLES of 1780, as having been completed about that Time, being rendered more exact than the former by the Addition of eight Equations to the Number in MAYER'S Tables, taken from MAYER'S Theory as to the Arguments, but settled as to the Maxima, from the said Observations, and the whole being calculated to Tenths of a Second. However the 18th Equation of these Tables was not used, as it was doubtful whether such an Equation should arise from the Theory of Gravity. Moreover the Epochs of the Sun's Longitude in MAYER's Tables, and of the Moon's Longitude and mean |