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A: Transverse fulcrum
B: Micrometer screw
C: Micrometer screw knob
D: Housing for telescope level bubble
E: Eyepiece end of the telescope
F: Parallel eyepiece

Fig 5.5 Automatic Levels
The most common components of several types of levels are the telescopic sight
and spirit bubble vial.

a. The Telescopic Sight
The modern telescopic sight consists of the following components:

1. A reticule, which provides the cross hair, near the rear of the telescope tube.
2. A microscope or eyepiece which magnifies the cross hair, and which must be
focused on them according to the eyesight of the observer.
3. An objective lens at the forward end of the telescope, which forms an image
of the sight target within the telescope tube.
4. A focusing lens, which can be moved back and forth inside the scope to
focus the image on the cross hair.

Focusing a Telescoping sight:
Three steps are required to focus a telescopic sight for greatest accuracy.
1. Aim the telescope at the bright, unmarked object, such as the sky, and
regulate the eyepiece until the cross hair is in sharp focus.
2. Aim the telescope at the object to be viewed and, while keeping the eye
focused on the cross hairs, regulate the focusing lens until the object is clear.
3. Eliminate parallex.

The Line Of Sight
A straight line from any point on the image through the optical center of the
objective lens will strike a corresponding point on the object. A straight line from
the cross hairs through the optical center of the lens will strike the point on the

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