Characteristics of striæ in optical glass . ?Stri(2 in large photographic lens train the authors demonstrated visually to their own satifactionthat only relatively heavy striae were an appreciable drawback tothe performance of the prisms and lenses tested. In fact, of thelot of six prisms shown only No. i was really very bad in its per-formance, and the striae in the lens of Fig. 8 seemed to exert nonoticeable effect upon the definition. To obtain a record of the amount of light scattered by the striaein these prisms, each one was inserted in a train otherwise good, 86 Scientific Papers of the
Characteristics of striæ in optical glass . ?Stri(2 in large photographic lens train the authors demonstrated visually to their own satifactionthat only relatively heavy striae were an appreciable drawback tothe performance of the prisms and lenses tested. In fact, of thelot of six prisms shown only No. i was really very bad in its per-formance, and the striae in the lens of Fig. 8 seemed to exert nonoticeable effect upon the definition. To obtain a record of the amount of light scattered by the striaein these prisms, each one was inserted in a train otherwise good, 86 Scientific Papers of the Bureau of Standards [voi. i6 and then this was used as a part of an optical-projection systemto project a magnified image of an artificial star—or, perhaps, inthis case it would be more correct to say an artificial planet, forthe pinhole was about mm in diameter—on a photographicplate. Because of the fact that the binoculars are chromatically cor-rected for visual impression rather than for photographic record,. Fig. 17.—StricB in a 5-inch telescope lens orthochromatic plates were used, and a Wratten and WainwrightK^ screen, which absorbs strongly in the violet, was placed justbefore the pinhole. In order to give some idea of the relativeintensity of the scattered light to that of the central image, aseries of exposiures, shown in the sequence left to right (Fig. 3),was taken, starting with one-half second and doubling the timefor each successive one until the eighth exposure was for 64 seconds. Smith, Bennett,!Merritt J StricE in Optical Glass 87 In the case of prisms 3 and 4, the one-half-second exposure wasunintentionally omitted. It is apparent from these reproductions that the damage doneto the image by the prisms 4, 5, and 6, is hardly noticeable. Inthe case of prisms 2 and 3 the scattered light is pronounced, butit is apparent from the figure that the central spot is relativelymuch more intense than the streamers of scattered light. Thisis, without doubt, the
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