A Treatise on Astronomy, Descriptive, Physical and Practical: Designed for Schools, Colleges, and Private Students |
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Page 13
... correct map of the visible heavens ; but to accomplish it , we must allow him at least one year's time , and even then he cannot arrive at anything like accuracy , as several incidental difficulties , instrumental errors , and practical ...
... correct map of the visible heavens ; but to accomplish it , we must allow him at least one year's time , and even then he cannot arrive at anything like accuracy , as several incidental difficulties , instrumental errors , and practical ...
Page 24
... correct , and the observa- tions correctly taken , all circumpolar stars would give the same , or very nearly the same , result . Such observations were made , and stars at the same distance from the pole gave the same latitude , and ...
... correct , and the observa- tions correctly taken , all circumpolar stars would give the same , or very nearly the same , result . Such observations were made , and stars at the same distance from the pole gave the same latitude , and ...
Page 26
... correct or allow for it . To determine the amount of refraction , we must resort to observations of some kind . But what sort of observations will meet the case ? Conceive an observer at the equator , and when the sun or mount of re- a ...
... correct or allow for it . To determine the amount of refraction , we must resort to observations of some kind . But what sort of observations will meet the case ? Conceive an observer at the equator , and when the sun or mount of re- a ...
Page 27
... correct his altitudes , and obtain his latitude , to considerable accuracy . Then , by repeating his observations , he can fur- ther approximate to the refraction . In this way , by a multitude of observations and computa- tions , the ...
... correct his altitudes , and obtain his latitude , to considerable accuracy . Then , by repeating his observations , he can fur- ther approximate to the refraction . In this way , by a multitude of observations and computa- tions , the ...
Page 30
... correct the altitude for refraction ( see table of refraction ) ; the difference will be the star's true altitude . clination of a star . Examples thod pursued If the true meridian altitude of the star is less than the meri- dian ...
... correct the altitude for refraction ( see table of refraction ) ; the difference will be the star's true altitude . clination of a star . Examples thod pursued If the true meridian altitude of the star is less than the meri- dian ...
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Common terms and phrases
altitude apogee apparent diameter argument argument of latitude ascending node astronomers attraction axis called celestial celestial equator central eclipse CHAP circle clock comet compute conceive conjunction corresponding declination degrees determine difference Digits eclipsed earth earth's orbit eccentricity equa equal equator equinox Evection fixed stars full moon give gravity greater greatest Greenwich heavens Hence horizon horizontal parallax inferior planet interval Jupiter Kepler's Kepler's third law less lunar orbit magnitude mass Mean Anomaly mean distance measure Mercury meridian altitude miles minutes MOON'S HOURLY MOTION moon's motion moon's path nearly node nutation observations opposite perigee period planet pole position proportion radial force radius refraction represent result revolution right angles right ascension round satellites Saturn semidiameter sidereal sine solar sun and moon suppose tance tangent telescope tion transit triangle true tude Uranus variation velocity Venus zenith
Popular passages
Page 144 - Jupiter a moderate-sized orange, in a circle nearly half a mile across; Saturn a small orange, on a circle of four-fifths of a mile; Uranus a full-sized cherry, or small plum, upon the circumference of a circle more than a mile and a half, and Neptune a good-sized plum on a circle about two miles and a half in diameter.
Page 139 - ... appearances of spots seen upon them, render it extremely probable that they subsist in the atmosphere of the planet, forming tracts of comparatively clear sky, determined by currents analogous to our trade-winds, but of a much more steady and decided character, as might indeed be expected from the immense velocity of its rotation. That it is the comparatively darker body of the planet which appears in the belts is evident from this, — that they do not come up in all their strength to the edge...
Page 143 - Venus a pea, on a circle 284 feet in diameter; the Earth also a pea, on a circle of 430 feet; Mars a rather large pin's head, on a circle of 654 feet; Juno, Ceres, Vesta, and Pallas, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange, in a circle nearly half a mile across...
Page 80 - For, by the first of Kepler's laws, the areas described by the radius vector are proportional to the times, and when this is the case, by Art.
Page 118 - The squares of the times of revolution are to each other as the cubes of the mean distances from the sun.
Page 144 - As to getting correct notions on this subject by drawing circles on paper, or, still worse, from those very childish toys called orreries, it is out of the question.
Page 141 - ... and less strongly marked than those of Jupiter, and owing doubtless to a similar cause. That the ring is a solid opake substance, is shown by its throwing its shadow on the body of the planet on the side nearest the sun, and on the other side receiving that of the body.
Page 154 - ... is leaving behind, must seem gradually to approach, in the same manner as when we walk through a forest, the ranges of trees to which we advance are constantly widening in their apparent distance from each other, while the distance of those we leave behind is gradually contracting.
Page 147 - Gregorius, of Constantinople, in June, 1337, whose course he describes very accurately. Comets do not all move from west to east, like the planets. Some have a direct, and some a retrograde motion. Their orbits are not comprehended within a narrow zone of the heavens, like those of the principal planets ; they vary through all degrees of inclination. There are some whose plane is nearly coincident with that of the ecliptic, and others have their planes perpendicular to it. Indeed, a slight inclination...
Page 89 - Whenever the sun is above the horizon of any place, that place is receiving heat; when below, parting with it, by the process called radiation ; and the whole quantities received and parted with in the year...