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5. Checking and Adjusting Your Instrument
Although this instrument has been calibrated and adjusted before
shipping out of NWI, instruments may come out of calibration during
shipping. Because of this, we strongly suggest that you have this
instrument checked before use. The following procedures may help to
fulfill this purpose.
5.1 Plate Vial
Set up your instrument properly on the tripod. Adjust the leveling screws to
center the bubble in the plate vial. Turn the telescope 90
°
clockwise, check
the bubble position, and then, turn the telescope 90
°
counterclockwise and
check the bubble position again. If the bubble is off center, the plate vial
needs to be calibrated by a technician.
5.2 Check Instrument Calibration
1) Place two rods facing each other at points A and B at a distance of 50 - 80
m apart. Set up your instrument at point C, which is about halfway between
A and B.
2) Sight the rods and take readings on point A as A and from point B as B.
3) Set the instrument at point D, which is about 2 m from point A.
4) Sight the rods at point A, take reading as AA. And then, sight the rod at
point B, take reading again as BB.
5) Use the following equation to calculate:
BB' = AA - (A - B)
The instrument is in its perfect condition if BB' = BB, otherwise, it needs
calibration.
