The Stereo Dissection Microscope
The dissecting microscope is configured to allow low magnification
of three-dimensional objects- objects larger or thicker than
the compound microscope can accommodate. Furthermore, the two
separate lenses of the binocular dissecting microscope allow
one to see objects in three dimensions, i.e., in stereo. Dissecting
microscopes do not magnify to the extent of compound microscopes.
The microscope models
we have in the Biology Department magnify from about 10X up to
40X with either variable or zoom magnification.
Dissecting microscopes utilize two types of light: from incident
light (direct illumination) or from transmitted light. Opaque
objects placed on the microscope stage can be directly illuminated
with incident light from an illuminator. In this case the illuminator
can be mounted in an opening in the arm of the microscope, or
in an adapter ring attached to a separate illuminator base (transformer).
Alternatively, light from a source such as a lamp can be reflected
through a translucent object from underneath using the substage
mirror. This method of illumination requires the clear glass
insert in the microscope
stage. However, in most instances the opaque stage insert, which
has a white side and a black side, and direct lighting is most
commonly used. You likely will see different types
of illuminators avalable in lab.
- ALWAYS carry the microscope with TWO HANDS. This practice
helps prevent bumping and dropping accidents that jar lenses
out of alignment. Grasp the microscope arm with one hand and
support the microscope under the base with the other hand.
Remove the dust cover and put it in the microscope cabinet.
- Obtain a suitable specimen (object) to view, and place it
in a shallow container on the stage.
- Position the illuminator next to the microscope directing
the beam at the specimen, and turn it on. Many illuminators have
rheostats to allow adjustment of the intensity of the light.
Do not use more light than you need, as the image quality will
- Adjust the magnification to its lowest power with the magnification
knob on the top or side of the microscope body.
- Adjust the interpupillary distance of the ocular lenses.
Look through the ocular lenses. If you see one image, no adjustment
is necessary. If you see two images, or a lot of black, adjust
the distance between the ocular tubes until you see one image.
You also may need to move your eyes closer to or farther away
from the ocular lenses so that the specimen's image fills the
|You may need to adjust the ocular lenses far
apart or close together.
- Focus on the specimen. This is a two-step process. In the
first step, you will roughly focus on the specimen with the objective
lens. In the second step, you will compensate for any differences
in strength between your eyes to obtain the sharpest image possible.
- Rough focus
a. Lower the microscope body to its lowest point with the focusing
knob on the sides of the microscope arm. Use the focus knob to
raise the microscope body until the specimen image is the sharpest.
b. Compensate for any differences in strength between your eyes.
(The following directions are written for microscopes with diopter
adjustment rings on the right ocular tube. Obviously, if you
have a scope with the diopter adjustment on the left ocular tube,
you will start with your right eye closed.)
c. Close your left eye. Adjust the diopter adjustment ring until
the image is in focus for your right eye. You may want to adjust
the ring back and forth (i.e., in and out of focus) a few times
until you are sure you have the best focus for yourself.
d. The first time through the diopter adjustment you may want
to repeat steps a through d-sometimes our eyes automatically
compensate for out-of-focus images seen in the microscope, and
eyestrain results. Who wants a headache in bio lab??
- If you change the magnification, you may need to adjust the
When you are finished using the microscope:
- Turn off the illuminator. Unplug it, lightly wrap the cord
around it, and put it in the microscope cabinet.
- Clean the microscope stage - this is especially critical
if you have viewing marine specimens or have used corrosive chemicals
in your labwork.
- Lower the microscope body all the way down.
- Replace the dust cover.
- Return the microscope to the cabinet with two hands.
Created by Kathy
Department of Biology, Bates College, Lewiston, ME 04240