. The Boston school compendium of natural and experimental philosophy .. . h the object itselfis viewed, through the medium of a number of reflecting telescope is one in which the image of theobject is reflected from a concave mirror, within thetube of the telescope, and viewed through a number oflenses.* There are two kinds of refracting telescopes, called the astronom-ical telescope, or night glass, and the terrestial telescope, or In the former, or night glass, there are but two lenses orglasses, but the object is viewed in an inverted position. As theglass is used princ
. The Boston school compendium of natural and experimental philosophy .. . h the object itselfis viewed, through the medium of a number of reflecting telescope is one in which the image of theobject is reflected from a concave mirror, within thetube of the telescope, and viewed through a number oflenses.* There are two kinds of refracting telescopes, called the astronom-ical telescope, or night glass, and the terrestial telescope, or In the former, or night glass, there are but two lenses orglasses, but the object is viewed in an inverted position. As theglass is used principally for viewing the heavenly bodies, the inver-sion of the image produces no inconvenience. In the latter, or dayglass, two additional lenses are introduced to give the image its nat-ural position. Fig. 113 represents a night glass, or astronomical telescope. It consists of a tube, A B C D, containing two glasses, or lenses. The lens A B, having a longer focus, forms the object glass; the other lens, D C, is the eye glass. The rays from a very distant body, Fig. as a star, and which may be considered parallel to each other, are re-fracted by the object glass A B to a focus at K. The image is thenseen through the eye glass D C magnified as many times as the fo-cal length of the eye glass is contained in the focal length of the * The image of the object seen through a refracting telescope is never so clearand perfect as that obtained by the reflecting telescope ; because the dispersion ofcolors which every lens produces, in a greater or 1ss degree, renders the image dulland indistinct, in proportion to the number of lenses employed. t Some glasses or teleseopes are marked Night and Day. These have fourglasses, two of which can be removed when the heavenly bodies are viewed. 371. What is a telescope? How many kinds of telescopes are there? Whatare they ? What is a refracting telescope ? What is a reflecting telescope? Whyis the image of an object, seen through a refractin
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Keywords: ., bookcentury1800, bookdecade1830, booksubjectphysics, bookyear1837
