2. Adjusting the rack stop.
The 40X objective uses a retractable security system to avoid damage to the
specimen slide or to the front of the lens, should the two come into contact.
Additionally as a security measure, the microscope includes a rack stop screw that
regulates the upward movement of the stage. The rack stop screw comes pre-
adjusted by the factory for standard slides with a 0.17mm thick cover slip. However,
for observing other types of slides adjustment may be necessary.
a. Loosen the rack stop screw (Fig. 2).
b. With the fine focus knob (13) at mid-range, focus on specimen slide, using only
the coarse focus knob (12), firstly with the 4X objective, (4) then with the 10X.
c. Tighten the rack stop screw just until the stage (6) can not ascend.
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