Focusing the Nikon TE2000 Condenser

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The condenser will be at different levels for the dry and oil objectives. So it may be a good idea to check that it is in focus and centered when you start using the scope.

Steps

Note: It may be easier to do this using the eyepiece. Also, it is much easier to do this using a low mag objective, you may want to practice on the 10X dry the first time.

  1. Bring your sample into focus
  2. Shrink the condenser diaphram as small as possible
  3. Adjust the height of the condenser so that you see a gradient of light in the field.
  4. Adjust the height of the condenser such that the field grows darker, note the direction that the brighter part of the gradient is eminating from.
    • If the field is growing brighter it means that you are making the condenser more out of focus.
  5. Use the two screw on the face of the condeser to adjust the XY position of the condenser in the direction of the brighter part of the gradient, continue until you see a nice gradient again.
  6. Iterate the previous two steps until upon adjusting the height you see a sharp edge to the light coming from the condenser. The shape of the diaphram is an octagon.
  7. Use the screws to center the octogon and then open the condenser diaphram until it is just larger than the field of view.

Tips for oil immersion objectives

Due to the large appearance of the aperture on 60x and 100x objectives (i.e. even when the aperture is maximally closed, it is still larger than the field of view), it may be difficult to find the diaphragm edge. This technique, developed by Francois, may prove helpful:

  1. Switch to a 10x objective (note: you may need to remove the 60x objective so as not to crash it into the stage)
  2. Follow Steps above without any sample. Get a nice crisp octagon
  3. Switch back to your 60x objective, and without any sample, make sure that you have a nice crisp edge in your field of view (note: this may involve moving the XY position of the condenser diaphragm)
  4. Add your sample, and focus on an area with no or few cells. Cells diffract the light, and so the more cells you have in your field of view, the more difficult it will be to see the edge.
  5. Follow steps above.
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