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. 1902 Excerpt: ...it is horizontal, and the telescope and collimator adjusted by means of the screws bb until the image of the slit falls upon the intersection of the cross-hairs in the telescope. The telescope should then be turned about the axis of the instrument through any angle, and the prism turned through such an angle that the ...
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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. 1902 Excerpt: ...it is horizontal, and the telescope and collimator adjusted by means of the screws bb until the image of the slit falls upon the intersection of the cross-hairs in the telescope. The telescope should then be turned about the axis of the instrument through any angle, and the prism turned through such an angle that the light from the slit is so reflected from the prism face AB that the image of the slit again appears in the field of view of the telescope. In general this image of the slit will not fall upon the intersection of the cross-hairs. It should be made to do so by adjusting the leveling screws of the prism. The telescope is then turned so as to be perpendicular to the face AB of the prism. In order to set it accurately perpendicular to that face, it is necessary to illuminate the cross-hairs and observe their image reflected from the face AB. When this image coincideswith the cross-hairs themselves, the telescope is perpendicular to the face of the prism. The cross-hairs and their image should be brought into coincidence by adjusting the telescope. The telescope and prism should then be brought into their original positions, and the image of the slit observed directly. It will in general no longer fall upon the intersection of the cross-hairs. It should be made to do so by adjusting the collimator by means of the screw b. This operation must be repeated until the imaga of the slit remains on the intersection of the cross-hairs in all three of the positions. When this is accomplished the telescope and collimator are perpendicular to the axis of the instrument, and the prism face AB is parallel to that axis. It is then necessary to make the other face of the prism, namely AC, parallel to the axis CD. To accomplish this it is merely necessary to set tha...
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