The economy of the eyes |
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Page 59
... Star which accom- panies the Pole Star is one of the best Objects for ascertaining the relative power of Glasses for shew- ing faint points of Light - and is most convenient as the Telescope requires scarcely any motion to keep the ...
... Star which accom- panies the Pole Star is one of the best Objects for ascertaining the relative power of Glasses for shew- ing faint points of Light - and is most convenient as the Telescope requires scarcely any motion to keep the ...
Page 273
... Stars , like that which accompanies the Pole Star , & c . On the 2d of October , 1822 , between nine and ten in the evening , I compared a celebrated 7 feet Achro- matic with an aperture of 4 inches , with an excellent Gregorian of 3 ...
... Stars , like that which accompanies the Pole Star , & c . On the 2d of October , 1822 , between nine and ten in the evening , I compared a celebrated 7 feet Achro- matic with an aperture of 4 inches , with an excellent Gregorian of 3 ...
Page 274
... Star , near the Pole Star , uncom- monly plain . On the 9th May , 1824 , I compared a fine 44 inch Achromatic of 27ths aperture , with a Gregorian Reflector of 12 inches focus and of 4 inches aper- ture : Jupiter did not appear so white ...
... Star , near the Pole Star , uncom- monly plain . On the 9th May , 1824 , I compared a fine 44 inch Achromatic of 27ths aperture , with a Gregorian Reflector of 12 inches focus and of 4 inches aper- ture : Jupiter did not appear so white ...
Page 278
... Stars which accompany Rigel , the Pole Star , & c . can only be attributed to their want of Defining power yet Reflectors have only the difficulties of Workmanship to overcome , and those only in half the degree which Achromatics have ...
... Stars which accompany Rigel , the Pole Star , & c . can only be attributed to their want of Defining power yet Reflectors have only the difficulties of Workmanship to overcome , and those only in half the degree which Achromatics have ...
Page 280
... Stars , near the Pole Star , and near Rigel the Division in the Ring of Saturn - and distant objects in the Evening , which are dis- tinctly seen with a 5 feet Achromatic of 3ths inches Aperture , and an Illuminating power of 144 , are ...
... Stars , near the Pole Star , and near Rigel the Division in the Ring of Saturn - and distant objects in the Evening , which are dis- tinctly seen with a 5 feet Achromatic of 3ths inches Aperture , and an Illuminating power of 144 , are ...
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Common terms and phrases
27ths inches 3ths inches 46 inch aberration Achro Achromatic Telescope adjusted aperture of 3ths appear Astronomical Belts Bootis bright Cassegranian Celestial centre Chapter colour Concave construction Convex Defining power distance distinct distinctly Ditto Dollond Double Stars equal experiments Eye-piece Eye-tube feet Achromatic feet focus feet Newtonian feet Reflector feet Telescope field of view figure Finder fixed stars focal length fying power glass Gregorian Telescope HERSCHEL higher power Huygenian Illuminating power inches aperture inches focus inches in diameter Instrument Jesse Ramsden Jupiter large metal larger lens lenses less light Magnifying power matic mirror Moon Newtonian Reflector Newtonian Telescope object Object-glass observations Opticians Optics pencil of rays perfect perfectly Peter Dollond Phil Planet Pole Star proportion Reader Reflecting Telescopes Rigel Ring of Saturn Satellites scope screw seen shew Sir W. H. Sir Wm small speculum small Star Specula Tele tion tonian Trans tube TULLEY visible vision
Popular passages
Page 407 - Trace Science, then, with Modesty thy guide ; First strip off all her equipage of Pride ; Deduct what is but Vanity or dress, Or Learning's luxury, or Idleness ; Or tricks to show the stretch of human brain, Mere curious pleasure, or ingenious pain ; Expunge the whole, or lop th...
Page 13 - Prescrib'd her heights, and prun'd her tender wing, (Her guide now lost) no more attempts to rise, But in low numbers short excursions tries: Content, if hence th...
Page 7 - O, it is excellent To have a giant's strength ; but it is tyrannous To use it like a giant.
Page 303 - At one time, after sweeping a portion of the heavens with that instrument, he tells us that " the appearance of Sirius announced itself at a great distance like the dawn of the morning, and came on by degrees, increasing in brightness, till this brilliant Star at last entered the field of the telescope with all the splendour of the rising sun, and forced me to take my eye from the beautiful sight.
Page 359 - ... and satellites, and eclipsed by them : the most distant of the rings also turning upon its axis, and the same taking place with the farthest of the satellites : all the parts of the system of Saturn occasionally reflecting light to each other: the rings and moons illuminating the nights of the Saturnian : the globe and...
Page 238 - Whatever expense an instrument had cost in forming, if it did not fully answer the intended design, he would immediately say, after a little examination of the work, " Bobs, man ! this won't do, we must have at it again:" and then the whole was put aside, and a new instrument begun.
Page 384 - I resolved to examine every star in the heavens with the utmost attention and a very high power, that I might collect such materials for this research as would enable me to fix my observations upon those that would best answer my end. The subject has already proved so extensive and still promises so rich a harvest to those who are inclined to be diligent in the pursuit, that I cannot help inviting every lover of astronomy to join with me in observations that must inevitably lead to new discoveries.
Page 360 - These rings are at a considerable distance from each other, the smallest being much less in diameter at the outside than the largest is at the inside: the...
Page 237 - ... take his seat close to the kitchen fire-side, in order to draw some plan for the forming a new instrument, or scheme for the improvement of one already made. There, with his drawing implements on the table before him, a cat sitting on one side, and a certain portion of bread, butter, and a small mug of porter placed...
Page 384 - Herschel was himself the first to point out the discrepancy : — " As soon as I was fully satisfied that in the investigation of parallax the method of double stars would have many advantages above any other, it became necessary to look out for proper stars. This introduced a new series of observation. I resolved to examine every star in the heavens with the utmost attention and a very high power, that I might collect such materials for this research as would enable me to fix my observations upon...