The sidereal messenger of Galileo Galilei : and a part of the preface to Kepler's Dioptrics containing the original account of Galileo's astronomical discoveries . anets present their discs perfectlyround, just as if described with a pair of compasses,and appear as so many little moons, completely illu-minated and of a globular shape ; but the fixed starsdo not look to the naked eye bounded by a circularcircumference, but rather like blazes of light, shootingout beams on all sides and very sparkling, and with atelescope they appear of the same shape as when theyare viewed by simply looking at
The sidereal messenger of Galileo Galilei : and a part of the preface to Kepler's Dioptrics containing the original account of Galileo's astronomical discoveries . anets present their discs perfectlyround, just as if described with a pair of compasses,and appear as so many little moons, completely illu-minated and of a globular shape ; but the fixed starsdo not look to the naked eye bounded by a circularcircumference, but rather like blazes of light, shootingout beams on all sides and very sparkling, and with atelescope they appear of the same shape as when theyare viewed by simply looking at them, but so muchlaro^er that a star of the fifth or sixth mao^nitudeseems to equal Sirius, the largest of all the fixed ^Telescopic But bevoud the stars of the sixth mao-nitude you Stare • tKpIr J O J will behold through the telescope a host of other stars, 1 The immense distance of stars makes it impossible for them to bemagnified by any telescope, however powerful; the apparent or spuriousdisc is an optical effect, which depends on the telescope used, and issmallest with the largest aperture. Stars : theirinfinite Or(ons 6e/f and Sword; 83 Stars. Pleiades, 3b StarsGalileo^Sidereus Nunc/us. THE SIDEREAL MESSENGER. 41 wliicli escape tlie unassisted sio;lit, so numerous as to multitude. -L - As examples, be almost beyond belief, for you may see more than 0°^^ Beit •J J J J and Sword six otlier differences of mao-nitude, and tlie laro-est of ^^ the ^ ^ O _ Pleiades are these, whicb I may call stars of the seventh maoiii- described •^ *-^ as seen by tude, or of the first magnitude of invisible stars, ap- with the aid of the telescope larger and brighterthan stars of the second masfnitude seen with theunassisted sight. But in order that you may see oneor two proofs of the inconceivable manner in whichthey are crowded together, I have determined tomake out a case against two star-clusters, that fromthem as a specimen you may decide about the rest. As my f
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Keywords: ., bookauthorgalileigalileo1, bookcentury1800, booksubjectastronomy
