Elements of Astronomy: Accompanied with Numerous Illustrations, a Colored Representation of the Solar, Stellar, and Nebular Spectra, and Celestial Charts of the Northern and Southern Hemisphere |
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angle aphelion apparent motion apparent movements appear astronomers atmosphere attraction axis Boötes bright called celestial equator celestial pole celestial sphere centre changes circle clock color comet constellations density Describe determined diameter direction disk distance Earth Earth's orbit Earth's rotation Earth's surface equal equatorial eye-piece fact globe gravity heat heavenly body heavens hemisphere Hence horizon inclined inferior planet Jupiter latitude length lens light longitude lunar magnitude Mars mass mean Sun Mercury meridian meteors miles Moon Moon's move naked eye nearest nearly nebula Neptune night node northern object-glass observed Orion parallax path perihelion period photosphere polar position prism rays refraction represented revolution revolve round right ascension ring round the Sun satellites Saturn seen shadow sidereal solar day solstice southern spectrum spots stars Sun's superior planet suppose tance telescope tion Uranus Ursa vapor variable stars velocity Venus vernal equinox visible zenith zenith-distance
Popular passages
Page 20 - A sphere is a solid bounded by a curved surface, every point of which is equally distant from a point within called the center.
Page 20 - Every circumference of a. circle, whether the circle be large or small, is supposed to be divided into 360 equal parts called degrees. Each degree is divided into 60 equal parts called minutes, and each minute into 60 equal parts called seconds.
Page 274 - Effect of Distance. — A body at the surface of the Earth, or 4,000 miles from its centre, acquires, as we have seen, by virtue of the Earth's attraction, a velocity of 32| feet per second at the end of the first second. During this second, however, it has not fallen 32| feet ; for, as it started from a state of rest, and acquired the velocity of...
Page 151 - A man placed on one of them would spring with ease 60 feet high, and sustain no greater shock in his descent than he does on the earth from leaping a yard.
Page 130 - Almost directly preceding, or at 270°, appeared a bluntly triangular pink body, suspended, as it were, in the corona. This was separated from the moon's edge when first seen, and the separation increased as the moon advanced. It had the appearance of a large conical protuberance, whose base was hidden by some intervening soft and ill-defined substance...
Page 128 - Moon's shadow sweeps across the surface of the Earth, and is even seen in the air ; the rapidity of its motion and its intenseness produce a feeling that something material is rushing over the Earth at a speed perfectly frightful.
Page 249 - The geocentric latitude, on the other hand, is the angle made at the centre of the earth (as the word implies) between the plane of the equator and a line drawn from the observer to the centre of the earth, which line of course does not coincide with the direction of gravity, since the earth is not spherical.
Page 71 - Besides the eight principal planets mentioned above, a ninth — quite small — is suspected to exist, between Mercury and the Sun, only thirteen million miles from the latter, and performing its revolution in about 19f days, in an orbit inclined to the ecliptic at an angle of 12°. A French physician, named Lescarbault, claimed to have discovered it crossing the Sun's disk in 1859. The name of Vulcan was assigned to it. Other observers have, at different times, seen spots of a planetary character...
Page 235 - Bearing in mind that what an astronomer wants is a good clear image of the object observed, we shall at once recognise that magnifying power depends upon the perfection of the image thrown by the object-glass and upon the illuminating power.
Page 61 - We may begin by saying, that the whole surface of the Sun, except those portions occupied by the spots, is coarsely mottled; and, indeed, the mottled appearance requires no very large amount of optical power to render it visible. It has been often observed with a good refractor of only 2£ inches aperture. Examined, however, with a large instrument, it is seen that the surface is principally made up of luminous masses — described by Sir W. Herschel as