9
horizontal. The press button also verifies the leveling up of the
ESL2
’ because the staff image will not show the correct movement on
pressing the button if the circular bubble is long away from its central
position, but the movement will be quicker and shorter due to the
pendulum reading its stop.
The eyepiece(6) with dioptric scale is turned to focus the reticle cross hairs.
After turning the bayonet locking ring anticlockwise, the eyepiece can be
removed and replaced by an optional eyepiece.
The reticle has wedged-shaped hairs for precise leveling with the parallel
plate micrometer, and a single horizontal hair for normal leveling staffs. It
also has 1:100 stadia hairs(6.2).
The focusing knob(10) is turned to obtain a sharp image of the staff. It has
a coarse and fine motion. Rotation of the instrument is friction-braked.
Fine-pointing is by means of the endless horizontal drive screw(3). The
drive has knobs at each side for use with either hand.
4.2 Leveling Staffs
As the telescope of the
ESL2
gives an erect image, leveling staffs with erect
numbers should be used. It is emphasized that the accuracy of leveling
depends just as much on the staffs as on the level.
