Explain the temporary adjustment of transit theodolite
1 Answer
Answer :
Temporary adjustment of transit theodolite consists of following steps.
1. Setting up theodolite over a station
2. Levelling up
3. Focusing of eyepiece.
4. Focusing of object glass.
1. Setting up theodolite over a station
Setting up the theodolite includes following process:
a) Centering the instrument over station point.
Centering of theodolite is carried out by suspending a plumb bob form hook exactly over a station point.
b) Levelling the instrument approximately by tripod leg.
2. Levelling up
Accurate leveling with the help of foot screw includes following steps:
a) Turn the theodolite about its vertical axis until the plate level is parallel to any pair of leveling screw.
b) Move the foot screw either both in outward or inward directions by same amount until the bubble comes in the center of their run.
c) Rotate the telescope by 90° and the bring it over the third foot screw and bubble is brought in center by operating third foot screw.
d) Again bring the telescope back to its original position and repeat the steps ‘b’ and ‘c’ until the bubble remains at center in both the positions.
e) Now turn the telescope in any third position through 360 °and observe the bubble, if it is remain in center , then the theodolite in accurate leveling.
3. Focusing of eyepiece.
Focusing of eyepiece enables to make the cross hair clear and distinct.
This is achived by holding the white paper in front of object glass and the eyepiece is rotated in clockwise or anticlockwise direction till the cross hair are clear and sharp.
4. Focusing of object glass.
Object of focusing of object glass is to bring the image of object formed by the object glass in the plane of the cross hair.
To eliminate parallax , direct the telescope towards object and turn the focusing screw until the appears clear and sharp.