OBN-14-BA-e-1510
14
5.2 (Pre-) focussing
When you are observing an object, you must have the correct distance to the
objective to achieve a sharp image.
In order to find this distance at the beginning (without other default settings of the
microscope) place the objective with the lowest magnification in the beam path, look
through the right eyepiece with the right eye and turn it slowly using the coarse
adjustment knob
(see illustration)
.
The simplest way of doing this would be to first raise the specimen stage (using the
coarse adjustment knob) until it is just under the objective and then lower it slowly. As
soon as an image is recognisable (no matter how sharp), then you should only adjust
the focus using the fine adjustment knob.
Adjusting the torque of the coarse and fine adjustment knob
Next to the left adjustment wheel for the coarse and fine adjustment knob there is a
ring which you can use to alter the torque of these wheels. Turning it in a clockwise
direction reduces the torque and turning it in an anti-clockwise direction increases it.
On one hand, this function can help to make it easier to adjust the focus and on the
other hand it can prevent the specimen stage from slipping down unintentionally.
Important:
In order to avoid damaging to the focussing system, the left and right adjustment
wheels for the coarse and fine adjustment knob must never be rotated at the same
time in opposite directions.
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