Page:The wonders of optics (1869).djvu/169

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THE TELESCOPE

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scope has the appearance of a very stumpy-looking refracting instrument, but one instant's examination will show the observer that the usual object-glass is absent at the end of the tube. In fig. 45 we have a Gregorian telescope, mounted on a tripod stand.

Fig. 45.—Gregorian Telescope.

Whilst experimenting on the Gregorian telescope, Newton made certain improvements in its construction, which we shall proceed to describe. A glance at

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