Jones, H. Spencer (Harold Spencer), 1890- · London E. Arnold & co. · leaf 202
. It is usual to provide any instrument with several eye-piecesof different focal lengths, so enabhng the magnification whichis most suitable for any particular observation to be used.It must be emphasized, however, that increase of magnifica-tion for an object-glass of given aperture does not… … Mount Wilson Oiiskkna toky ioo-inlii Ki;i.T.K(r()K. ASTRONOMICAL INSTRUMENTS 171 at the time of observation—beyond which it is inadvisableto increase the magnification. 96. The Transit Instrument.—This instrument, which isused for the determination of sidereal time, is necessarily oneof the…
Astronomy
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