20
opposite rotations.
1.2 Turn the alidade through 90°in a clockwise direction and centre the bubble with
footscrew C.
1.3 Turn the alidade clockwise through 180°. Note the position of the bubble. Bring
the bubble to a point halfway between this position and the central position by
turning footscrew C. Now, with an adjusting pin, carefully turn the adjustment screw
(12) until the bubble is centred.
1.4 Repeat until bubble remains centred within one division for positior of the
alidade.
