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theodolite 
Sighting instrument that is used especially in astronomy, geodesy and navigation for measuring horizontal and vertical angles.
alidade level
Transparent tube that contains liquid and an air bubble; it serves as a guide for positioning the alidade on the vertical axis.
illumination mirror
Adjustable polished glass surface that reflects light onto the circles so that the angles can be read.
leveling head
Platform serving as a support for the theolodite.
horizontal clamp
Knob that locks the alidade to prevent it from rotating.
leveling head locking knob
Knob that locks the alidade to the leveling head.
leveling head level
Transparent tube that contains liquid and an air bubble; it serves as a guide for positioning the leveling head on the horizontal axis.
base plate
Plate to which the leveling head is attached by means of three leveling screws.
leveling screw
Screw that adjusts the theodolite’s leveling head level on the horizontal plane.
telescope
Optical instrument composed of several lenses; it can be adjusted in the horizontal and vertical planes and is used to observe distant objects.
optical sight
Device with an eyepiece that precisely aims the telescope at the target whose angles are to be measured.
adjustment for horizontal-circle image
Knob that adjusts the sharpness of the image of the horizontal circle (graduated from 0° to 360°) in order to read the angles on the horizontal axis.
micrometer screw
Knob that adjusts the micrometer to give a very precise reading of the circles’ measurements.
adjustment for vertical-circle image
Knob that adjusts the sharpness of the image of the vertical circle (graduated from 0° to 360°) in order to read the angles on the vertical axis.
alidade
Part of the theodolite that rotates on a vertical axle to measure angles by means of the telescope.
