This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 edition. Excerpt: ...mirror 5 was secured against a plate of aluminum 4 which could be tilted forward and backward by virtue of the hinge 7. The tilting was controlled by the spring 9 and the screw 10. Gross movements of the mirror about the vertical axis could be made / by releasing the clamping screw 14. Finer adjustments were ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 edition. Excerpt: ...mirror 5 was secured against a plate of aluminum 4 which could be tilted forward and backward by virtue of the hinge 7. The tilting was controlled by the spring 9 and the screw 10. Gross movements of the mirror about the vertical axis could be made / by releasing the clamping screw 14. Finer adjustments were made by g means of the screw II 5 4 and the spring 12, after securing the screw 13. For all observations made after April 28, the mirror and mount were secured to a concrete pier 1. A commercial plateglass mirror was used in preliminary trials and found very unsatisfactory. At a distance of 600 m ' several images of the light source could be seen. This made it diflicult to judge when the mirror was adjusted and also caused very irregular effects on slight movements of the mirror. Mirrors made from optical flats silvered on the front surface were suggested. Such a flat of plate glass (2.5 cm thick and 25 c1n diameter) was secured from the optical shop of the Bureau, and another flat (2.5 cm by 30 cm) was loaned by R. W. Porter for this purpose. Both of these were true planes to within one-quarter wave length across the entire surface. Trials with the smaller fiat proved to be satisfactory in all respects, except that it tarnished very readily. Considerable preliminary data and some reported below were obtained with it. Because of the uncertainty arising from the F10. ro.---Ms'r1or and mounting at distant station decreasing reflecting power of the tarnishing surface, however, a portion of a mirror from a range finder used in military aeronautics was tried. This mirror, made by W . H. Taylor, of this Bureau, was silvered on the back, since its surfaces were very closely plane parallel. Although it was found to be slightly cylindrical...
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