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y of the year, with other numerical data, for the use of the astronomer and navigator; an astronomical almanac; as, the "American Ephemeris and Nautical Almanac."

The small distortion of an astronomical instrument caused by the weight of its parts; the amount to be added or substracted from the observed readings of the instrument to correct them for this distortion. The flexure of a curve (Math.), the bending of a curve towards or from a straight line.

A treatise on this science. Astronomical, or Mathematical, geography treats of the earth as a planet, of its shape, its size, its lines of latitude and longitude, its zones, and the phenomena due to to the earth's diurnal and annual motions. -- Physical geography treats of the conformation of the earth's surface, of t…

r result is effected; a tool; a utensil; an implement; as, the instruments of a mechanic; astronomical instruments. All the lofty instruments of war. Shak.

with a filar micrometer, used chiefly for reading and subdividing the divisions of large astronomical and geodetical instruments. -- Micrometer screw, a screw with a graduated head used in some forms of micrometers. -- Position micrometer. See under Position. -- Scale, or Linear, micrometer, a minute and very delic…

especially, one engaged in, or trained to habits of, close and exact observation; as, an astronomical observer. The observed of all observers. Shak. Careful observers may foretell the hour, By sure prognostic, when to dread a shower. Swift.

An ideal surface, conceived as coinciding with, or containing, some designated astronomical line, circle, or other curve; as, the plane of an orbit; the plane of the ecliptic, or of the equator.

m, or having a common radiating point; as, polar coördinates. Polar axis, that axis of an astronomical instrument, as an equatorial, which is parallel to the earths axis. -- Polar bear (Zoöl.), a large bear (Ursus, or Thalarctos, maritimus) inhabiting the arctic regions. It sometimes measures nearly nine feet in lengt…

finder. See under Range. -- Position micrometer, a micrometer applied to the tube of an astronomical telescope for measuring angles of position in the field of view. -- Single position (Arith.), the method of solving problems, in which the result obtained by operating with an assumed number is to the true result as…

Prussian; -- applied to certain astronomical tables published in the sixteenth century, founded on the principles of Copernicus, a Prussian.

One who accepts the astronomical system of Ptolemy.

The calculation of a ship's position, either from astronomical observations, or from the record of the courses steered and distances sailed as shown by compass and log, -- in the latter case called dead reckoning (see under Dead); -- also used fro dead reckoning in contradistinction to observation.

us consideration; reflective; contemplative; as, a reflecting mind. Reflecting circle, an astronomical instrument for measuring angless, like the sextant or Hadley's quadrant, by the reflection of light from two plane mirrors which it carries, and differing from the sextant chiefly in having an entire circle. -- Refle…

sage through the earth's atmosphere; -- hence distinguished as atmospheric refraction, or astronomical refraction.

A clock, or other timepiece, used as a standard of correct time. See Astronomical clock (a), under Clock.

Pertaining to, or designating, a set of astronomical tables computed by Kepler, and founded on the observations of Tycho Brahe; - - so named from Rudolph II., emperor of Germany.

A Chaldean astronomical period or cycle, the length of which has been variously estimated from 3,600 years to 3,600 days, or a little short of 10 years. Brande & C.

An astronomical instrument, the limb of which embraces a small portion only of a circle, used for measuring differences of declination too great for the compass of a micrometer. When it is used for measuring zenith distances of stars, it is called a zenith sector. Dip sector, an instrument used for measuring the dip of…

numbers (Arith. & Alg.), those fractions whose denominators are some power of sixty; as, astronomical fractions, because formerly there were no others used in astronomical calculations. -- Sexagesimal, or Sexagenary, arithmetic, the method of computing by the sexagenary scale, or by sixties. -- Sexagesimal scale (Ma…

stant, in which the heavenly bodies appear to have their places, and on which the various astronomical circles, as of right ascension and declination, the equator, ecliptic, etc., are conceived to be drawn; an ideal geometrical sphere, with the astronomical and geographical circles in their proper positions on it.…