NAUTICAL ALMANAC

AND

ASTRONOMICAL EPHEMERIS

FOR THE YEAR

1830.

PUBLISHED BY ORDER OF THE

COMMISSIONERS OF LONGITUDE.

London:

PRINTED BY T. BENSLEY, CRANE COURT, FLEET STREET,

PRINTER,

AND SOLD BY JOHN MURRAY, ALBEMARLE STREET,

BOOKSELLER

TO THE COMMISSIONERS.

1827.

[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 Sixty 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 the Tables of Dr. MASKELYNE, Dr. PEARSON, Mr. GROOMBRIDGE, and Mr. BAILY.

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