Correction for trunnion axis tilt
The trunnion axis tilt error is the deviation of the trunnion axis of the telescope from its required position at right angles to the plumb axis of the instrument.
| 1 | Trunnion axis tilt error |
In the instrument, perform a pre-measurement trunnion axis tilt test to determine the trunnion axis tilt error. Angular measurements are observed in both instrument faces, the trunnion axis tilt error is calculated, and the respective correction value is stored in the instrument. The trunnion axis tilt correction value is then applied to a correction to the horizontal angle value
Carry out a trunnion axis tilt test in the following situations:
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Whenever the instrument may have been roughly handled during transport.
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When the ambient temperature differs by more than 10°C (18°F) from the previous collimation test.
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Immediately before high-precision angle measurements in one face, especially where the vertical angles significantly deviate from the horizontal plane.
