Instruction

View in eyepiece

4.Center the diaphragm in the field of view by rotating the condenser adjusting screws. In other words, you adjust the illuminating path so that it is properly aligned along the optical axis of the microscope.

5.Open the luminous-field diaphragm by turning the adjustment wheel counter- clockwise until the edges just disappear from the field of view. This step ensures that you only illuminate the field- of-view.

6.Pull out one ocular and look through the eyepiece tube. Close the aperture diaphragm by turning the wheel in the condenser until the aperture is about 80% of the diameter of the objective pupil. Replace the eyepiece. Another way of adjusting the aperture is by looking at your specimen and closing the diaphragm until resolution and contrast are optimal. Diaphragm too open: poor contrast. Diaphragm too closed: poor resolution.

When adjusting Koehler illumination for higher magnification objectives, repeat the procedure. For lower magnifications (5x and 2.5x), the condenser performance is changed by the removal of the swing-out lens from the light pathway, and the condenser aperture diaphragm no longer controls the numerical aperture. Fully open the aperture diaphrgam and control the contrast by opening/closing the field diaphragm.