ADJUSTING THE HORIZONTAL AXIS

ADJUSTING THE TELESCOPE LEVEL - 14070_118

Engineering Aid 1 - Advanced Structural engineering guide book
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Figure 6-6.—Adjusting the line of sight. 4. Repeat this process until the condition is connected. NOTE: To compensate for the above maladjust- ment, use only that part of the vertical hair that is closest to the horizontal cross hair. ADJUSTING THE LINE OF SIGHT.— In a perfectly adjusted telescope, the line of sight should be perpendicular to the horizontal axis at its intersection with the vertical axis. To make the line of sight perpendicular to the horizontal axis (fig. 6-6), you should proceed as follows: 1. Sight on a point, A, at a distance of not less than 200 feet with the telescope normal; clamp both plates. 2. Plunge the telescope and set another point, B, on the ground at a distance from the instrument equal to the first distance and at about the same elevation as point A. 3. Unclamp the upper motion, rotate the instrument about its vertical axis, sight on the first point (telescope inverted), and clamp the upper motion. 4. Plunge the telescope and observe the second point. If the instrument is in adjustment, the point over which it is set will be on a straight line, AE, and point B will fall at position E. If the instrument is not in adjustment, the intersection of the cross hairs (point C) will fall to one side of the second point, B. Figure 6-7.—Adjusting the horizontal axis. 5. Measure the distance BC and place a point, D, one fourth of this distance back toward the original point, B. 6. Move the cross-hair reticle horizontally by loosening the screws on one side of the telescope tube and tightening the opposite screw until the vertical cross hair appears to have moved from C to the corrected position, D. 7. Repeat this operation from number 1 above, until no error is observed. 8. Repeat the test described for adjusting the vertical cross hair, since the vertical cross hair may have rotated during this adjustment. NOTE: You can compensate for the above maladjustment by double centering (discussed in the EA3 TRAMAN). ADJUSTING THE HORIZONTAL AXIS.— When you plunge the telescope, the line of sight should generate a truly vertical plane. For this to occur, the horizontal axis of the telescope must be perpendicular to the vertical axis. To make the horizontal axis of the telescope perpendicular to the vertical axis (fig. 6-7), you should perform the following steps: 6-7

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