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103
9. Troubleshooting
Problem
Bright field
The specimen can not be brought into focus.
Dark Field
No definite DF contrast is possible.
The image is unevenly or not uniformly illumi-
nated.
Undesirable stray light.
Cause/Remedy
Use the correct immersion medium.
Place the specimen on the stage with the cov-
erslip facing down.
Make sure that the cover glass thickness is
correct and that it suits the indication on the
objective.
Ensure that you are using an objective with
coverslip correction.
Adjust the correction ring on the objective if
present.
Be sure that a DF objective is being used.
The objective aperture is too high:
maximum 0.7 for condenser S1
maximum 0.4 for condenser S23/28
If necessary, reduce the objective aperture
using the iris diaphragm on the objective.
Check the condenser centering.
The magnification is too weak.
Use a higher magnification.
Remove the condenser head or condenser
lenses.
Clean the specimen and neighboring lenses
(→
p. 107).