20
Fig.5 Adjusting the circular bubble.
As an adjustment screw is tightened the
bubble runs towards it and, as it is loosened,
the bubble runs away from it. The first
adjustment screw to be turned, therefore, is
the one that is the nearest to being in line with the middle of the bubble and
the centre of the setting circle. It is turned only until the bubble reaches the
centre of the circle or until it can be set in the centre by means of the other
screw. It is necessary to complete the adjustment that the screws must not be
tuned more than. The circular bubble is in correct adjustment when it stays in
the centre of the circle in whatever direction the telescope is pointing. Keep
the circular level in adjustment, thereby ensuring that the compensator will
always be well within its working range.
