11
BM-300
Turn the coarse focus knob
①
conversely to
lower the specimen and search images in the
10
×
ocular simultaneously, and then use the fine knob
②
to focus. After that, you can replace with other
magnification objectives safely, and focus without the
risk of damaging the specimen.
To make the observation more convenient, you
can use the locking set
③
to fix the stage in a
vertical direction.
3.3.4 Condenser Adjustment
（
Fig.20
）
Turn the condenser focus knob to move the
condenser up and down. Raise the condenser when
using the high magnification objective, and descend it
when using the low magnification one.
The condenser and the objective are coaxial. It
has been adjusted before leaving factory, so
the user needn’t to adjust them by self
The highest position of the condenser has been
adjusted too. It also needn’t any user’s
operation
.
3.3.5 Aperture Iris Diaphragm Adjustment
（
Fig.20
）
Turn the aperture iris diaphragm collar
①
to
adjust the aperture iris diaphragm.
The aperture iris diaphragm is designed for
the adjustment of the numerical aperture
,
not for
the brightness.
Generally, setting the aperture iris diaphragm
to 70- 80% of the N.A. of the objective in use will
provide an image with good contrast. If you want
to observe the image of the aperture iris
diaphragm, remove one eyepiece and look through
the tube. You will see a dark circle encroaching on
the bottom of the tube.
Fig.17
Fig.18
Fig.16
