How to Properly Focus a Microscope
Set Up
Note: There is a diagram on the back of this page with all parts of the microscope labeled.
1. Pull down the electric cord closest to your table. Wrap the cord around a table leg to secure it.
2. Note how the microscope has been put away in the cabinet – it should look like that when you
are finished.
3. Carefully pull the microscope out of the slot, holding the arm of the microscope with one hand
and placing your other hand under the base.
4. Holding the microscope upright in front of you, walk back to your table.
5. Place the microscope completely on the table, plug in the microscope & when you are ready,
turn on the light.
6. Be sure the shortest objective lens (scanner – 40X) is in place and put the slide on the stage.
7. Try to move the slide so the object you are trying to see is in the center of the opening on the
stage.
8. Using the course adjustment knob and looking from the side, move the objective lens as close to
the slide as possible.
9. Now, look into the microscope and slowly FOCUS AWAY from the slide. When you think you see
something, stop, switch to the fine adjustment turn very slowly and bring it into clear view.
Move the slide slowly if needed with your thumbs.
10. If you need more or less light, change the diaphragm setting. It is a disk located just under the
stage.
What if…
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The lenses are dirty? Clean ONLY with lens tissue! If none is available, ask the teacher.
I can’t see anything? Check to see that the lenses &/or diaphragm is clicked into place.
11. Once you have the object focused and in the center of your field of view (the circle of light), look
from the side and carefully switch to the next longest lens (low power – 100X). These
microscopes are designed to keep an object in good focus as you change from one lens to
another.
12. Look through the eyepiece, you should still be in focus. If not turn the fine adjustment if needed
very slowly. If you want to see more detail, be sure to move the object to the center of the field
of view, then look from the side and carefully change to the longest lens (high power – 400X).
13. Focus with the fine adjustment, very slowly if needed. You may still move the slide, but because
it is so highly magnified, remember, a little move goes a long way! Call your instructor over to
verify you are in focus. The instructor will give you a lab packet and sign off on it that you
completed this part of the assignment.
14. Follow the clean-up procedures on the back of this page.
Parts of the Microscope Labeled…
Clean Up
1. When finished, be sure to remove the slide and put it away as directed.
2. Turn off the light, unplug the microscope and wrap the cord loosely around the base.
3. Make sure the shortest lens (scanner) is in place and that the eyepiece is turned over the arm
(unless you have a straight-tube microscope).
4. As you pick up your microscope by the arm, be cautious putting your other hand under the base
– it could be hot from the light being on.
5. Put the microscope away in the proper compartment the same way it was when you started.
6. Recoil the electric box near your table.
7. You are now ready to begin reading the lab that your instructor gave you. All pre-lab discussions
must be done by the end of the period and verified.
8. Homework: Re-read the lab tonight and be ready for a pre-lab quiz