A Manual of Spherical and Practical Astronomy: Spherical astronomy

Front Cover
J. B. Lippincott & Company, 1863
 

Other editions - View all

Common terms and phrases

Popular passages

Page 84 - Two follow-up urines should be obtained within one week after receipt of the original results, one at the beginning and the other at the end of the work week.
Page 673 - The squares of the periods of revolution of any two planets are proportional to the cubes of their mean distances from the sun.
Page 317 - CHAPTER VII. FINDING THE LONGITUDE BY ASTRONOMICAL OBSERVATIONS. 213. THE longitude of a point on the earth's surface is the angle at the pole included between the meridian of the point and some assumed first meridian. The difference of longitude of any two points is the angle included by their meridians. These definitions have been tacitly assumed in Art. 45, where we have established the general equation L = T0 — T (382) in which (Art.
Page 23 - The right ascension of a point of the sphere is the arc of the equator intercepted between its circle of declination and the vernal equinox, and is reckoned from the vernal equinox eastward from 0° to 360°, or, in time, from 0* to 24''.
Page 425 - If, then, the navigator can project this small circle upon an artificial globe or a chart, the knowledge that he is upon this circle will be just as valuable to him in enabling him to avoid dangers as the knowledge of either his latitude alone or his longitude alone; since one of the latter elements only determines a point to be in a certain circle, without fixing upon any particular point of that circle.
Page 129 - The atmosphere, however, is not of uniform density, but is most dense near the surface of the earth, and gradually decreases in density to its upper limit, where it is supposed to be of such extreme tenuity that its first effect upon a ray of light- may be considered as infinitesimal. The ray is therefore continually passing from a rarer into a denser medium, and hence its direction is continually changed, so that its path becomes a curve which is concave towards the earth. The last direction of...
Page 643 - This maximum corresponds, then, to the horizontal geocentric parallax ; and its effect upon the apparent places of stars might be investigated by the methods followed in Chapter IV. ; but we prefer to employ here the method just exhibited in the investigation of the aberration, on account of the analogy in the resulting formulae.
Page 53 - A sidereal day is the interval of time between two successive upper transits of the vernal equinox over the same meridian.
Page 172 - DIP OF THE HORIZON. Dip of the horizon is the angle of depression of the visible horizon below the true...
Page 242 - J t we must substitute k sin* (£ . fit), or, with sufficient precision, &// sin2 £ t. If the sun is observed with a mean time chronometer, the intervals are both to be corrected for rate and reduced from mean solar to apparent solar intervals. The mean interval differs from the apparent only by the change in the equation of time during the interval, and this change may be combined with the rate of the chronometer. Denoting by 8E the increase of the equation of time in 24* (remembering that E is...