State and explain temporary adjustments of dumpy level.

State and explain temporary adjustments of dumpy level.
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2 Answers

Answer :

1. Setting up the level: The instrument is set up on a tripod at convenient place.

Tripod legs should be set well apart for stability of instrument.

2. Leveling:

i) Approximate leveling: Approximate leveling is carried by tripod legs. For this two legs are firmly fixed and then third leg is moved circumferentially and inward/outward till bubble is approximately at center.

ii) Leveling by foot screws:

a. Bring all foot screws in their center of run.

b. Bring the telescope parallel to any two foot screws and rotate both screws either inward or outward to bring bubble in center.

c. Swing the telescope and bring the bubble over third foot screw. Center the bubble by rotating the third foot screw.

d. Repeat the steps b and c till bubble remain at center in both directions.

e. Swing the telescope through 1800 and check whether bubble remains at center.

3. Focusing eye piece:

i) Keep a piece of white paper in front of telescope or direct the telescope towards a clear sky.

ii) Adjust the vision by rotating eye piece till the cross hairs come into sharp and clear view.

4. Focusing the object: Direct the telescope towards the object (staff), rotate the focusing knob till object (staff reading) is in sharp view along with cross hair.

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Answer :

1. Setting up the level.

a. The level fixed on tripod.

b. The legs of tripod stand are well spread so that the level will remain stable on tripod.

c. Bring all the three foot screws in the centre of their run so that they can be turned clockwise or anticlockwise as required, for levelling purpose

d. Adjust the height of the instrument so that the observer can comfortably see through the telescope and note the readings.

e. Fix two legs of tripod and adjust third leg in such a way that the levelling head will become as horizontal as possible by eye judgment.

2. Levelling up the level.

a. The base of the tripod is already leveled with the help of cross bubble.

b. To make accurate adjustment of the level, the longitudinal level is adjusted in the centre of its run, with the help of three foot screws.

c. Make the bubble parallel to the any selected pair of foot screws. Now; turn both the foot screws either inward or outward with the help of foot screws till the bubble appears in the center.

d. Turn the telescope through 900 as shown in fig. below and now with the help of third screw bring the bubble of levelling tube in the center. 

image

3. Focusing the Eye piece.

a. Hold a sheet of white paper in front of the objective glass 4 to 6 cm away from objective glass and see through the eye piece.

b. Turn the eye piece inwards or outwards in the socket so that the cross hair on the diaphragm appears sharp and clear.

4. Focusing the Object glass.

a. Direct the telescope towards any object, say a levelling staff in the field which is kept at a distance. See through eyepiece whether the staff is visible, distinct or not.

b. If not, then turn the focusing screw till the image is distinct and clear. The cross hair on the diaphragm should also be seen clearly. 

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