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 by is a smaller dome. Off to the right is a substantial brick building evidently belonging to the observatory; and on reaching the top of the hill we see that behind, in the back yard so to speak, is a little cluster of domes, each surmounting a tiny building of its own. Of course our first desire is to see the large telescope, around whose pier the building was originally raised as a shelter. After climbing a few stairs, we find ourselves in a large circular room. Walls and ceiling are joined in one great curve,--in fact, they form the dome. This dome can be revolved on its “ball-bearings,” spheres of bronze which run in a circular track around the edge of the room. We do not notice this at once, however, for in front of us rises the magic instrument. It is a ponderous mass, and we question whether so great a weight can be controlled conveniently; but we find that it moves at a touch. There are certain difficulties in the use of so large a telescope, even if it is thus easily handled. In a large telescope, the apparent motion of the stars is so magnified that those at any distance from the pole seem fairly to rush across the field of view. Add to this the fact that the field of a large telescope is very small, and Professor Simon Newcomb may be understood when he says that with a telescope and nothing else one might spend a whole winter evening looking for Sirius, and on finding him, lose him at once and irrevocably. This difficulty of finding and keeping stars is obviated by the “equatorial” mounting, as well as by the “finders,” telescopes of low power and large field attached to the tube. \When a star is found, the instrument can be clamped so that it can be moved only in one direction — that of the star's apparent
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