Explain the repetition method for adjustment of horizontal angle?
Definition = the method in which the angle is measured in clockwise direction for any number of times is known as repetition method.
Usually six times three repetition with face left and three with face right.
- Set up instrument over Q and levelled with accurately with telescope in the normal position.
- Set up the Vernier A to 3600. Loosen the lower clamp direct the telescope to left hand ranging rod at P. exactly by using the upper clamp and lower tangent.
- The Vernier reading should be the same.
- Loose the upper clamp and turn the telescope in clockwise direction and bisect the right hand ranging rod at R exactly by using the upper clamp and upper slow motion screw.
- Read both Vernier. Let the mean reading be 3002’ the object of reading both the Vernier to obtain an approximate value of the angle.
- Leaving the Vernier unchanged unclamp the lower plate and turn the telescope in clockwise direction bisect the ranging rod P exactly with lower clamp and lower tangent screw. Reading of Vernier should be same as before.
- Loose the upper clamp and turn the telescope in clockwise direction and bisect ranging rod at R exactly by using upper clamp and upper tangent screw.
- The Vernier now read twice the value of angle
- By the levelling Vernier clamp at 60040’ measure the angle third time.
- Read both the Vernier’s. Read final angle.
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