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Koehler Illumination Instructions
1. Turn the scope power on, put your slide on the stage. You should use the 10x objective to start. Turn the light on.

2. Open the condenser and the field diaphragm all the way. The light level will get brighter.
  Microscope Components
Neutral Density Filters
3. Move the condenser up close to the slide, using the condenser focus knob. You will have to lower your head to see it.   Condenser focus knob
4. Focus your sample. Use the neutral density filters if the light to your eyes is too bright.   neutral density filters
5. Close the field diaphragm as far as it goes. You should see a small circle of light through the eyepieces.   small circle of light
6. Center the small circle using the condenser centering rods. This takes a little practice.   condenser centering rods
7. Focus with the condenser focus knob until you can see the blade edges. You will probably have to re-center it again after focusing the blade edges.   blades focused
8. Open the field diaphragm until it can't be seen through the eyepiece.

9. Take off one of the eyepieces and look through it as though you are looking at a TV screen. Close the condenser by about 10%. The diagram to the right shows approximately how it should look.
  through eyepiece

 

Proceed with your microscope session. For critical images, repeat this process at each magnification (e.g., 20x, 40x, etc.).

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