Elementary optics and applications to fire control instruments (1922)
United States. Army. Ordnance Dept · Washington, Govt. Print. Off. · leaf 69
will not shift when the gun is fired. In figure 65 the erecting system used is the second type of Porroprism. A perspective view of this is shown in figure 20. The relativepositions of the two upper polished faces are such that the system hasto be constructed in two pieces, which are either… … Fig. 65.—Telescope with second type of Porro erecting system of Porro prism and is not so generall}^ employed. At present it isfound in no fii-e-control instruments of American construction, but isused in the three-power observation telescopes which were purchasedfrom the French Government under…
Optics · Optical instruments · Fire control (Gunnery) -- Optical equipment
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