...Brewster readily admitted thata tube was not necessary, provided the focal image were conveyed into adark apartment and there properly received by reflectors... 
Richard A. Proctor 「Myths and Marvels of Astronomy」
...The diameter of this object-glass isthirty-six inches, and its focal length is fifty-six feet two inches...
Robert Stawell Ball 「The Story of the Heavens」
...The first was made with a Newtonian telescope something less than seven feet focal length, a power of 222, and an aperture of four and a half inches...
Edward Singleton Holden 「Sir William Herschel: His Life and Works」
...By reflection from this mirror the focal plane and theimages are shifted to F, where they may be examined fromone side through the magnifying glass E...
George C. Comstock 「A Text-Book of Astronomy」
...telescope having a focal length of8½ feet:...
Richard A. Proctor 「Half-hours with the Telescope」
...Both lenses have their convex surfaces toward theobject glass, and their distance apart is equal to half thesum of their focal lengths...
Garrett Serviss 「Pleasures of the telescope」
...'s work was continued for stars between δ = -2° andδ = -23° by , according to much the same plan, but witha larger instrument (aperture 159 mm, focal length 1930 mm, magnifyingpower 26 times)...
Carl Vilhelm Ludvig Charlier 「Lectures on Stellar Statistics」
..., focal length of200 mm...
Wm. Gaertner & Co. 「Astronomical Instruments and Accessories」
...5 feet focal length, and another, of 12 inches diameter and 18 feetfocal length, for Lamont, of Munich...
George Forbes 「History of Astronomy」
...In 1665 Cassini, with a fine telescope, 35-feet focal length, observedmany spots moving from east to west, whence he concluded that Jupiter rotateson an axis like the earth...
George Forbes 「History of Astronomy」
...'The whole immense powerof the telescope was applied, and to its focal image about one half ofthe power of the microscope...
Richard A. Proctor 「Myths and Marvels of Astronomy」
...On the other hand, the eye-glass mustnot be of such small focal length that the image appears indistinct andcontorted, or dull for want of light...
Richard A. Proctor 「Half-hours with the Telescope」
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