How to Use and Adjust a Compound Microscope

Step by Step.....Safely and Easily

Here are step-by-step instructions on how to use and adjust a compound microscope:

  1. Turn on the illuminator. When using the dimmer, it is best slowly increase the light intensity as the lamp heats up quite quickly.
  2. Place a slide or specimen on the stage with the sample directly above the aperture and, if possible, fasten it to the stage with the stage clips. Reminder: A cover slip is always needed to allow for the best quality image.


Ensure the iris diaphragm is completely open, allowing the maximum amount of light to reach the slide and the lenses. Caution: Do not use the iris diaphragm to control the light, it is to control resolution and contrast - use the dimmer instead.

lady looking through microscope


Rotate the nosepiece so that the objective lens with the lowest level of magnification is directly above the sample. Reminder: Using lower magnifications first helps to select the part of the specimen of interest and then adjust further.


Look through the binocular eyepieces and adjust the iris diaphragm until the amount of light is satisfactory. More light is better than less light, but the comfort of the viewer’s eyes should also be taken into account.


Turn the coarse adjustment knob until the specimen comes into broad focus. Caution: you should not use the coarse focus with a high magnification objective for fear of the objective making contact with the slide.


Turn the fine adjustment knob until the specimen comes into sharp focus. Caution: should not take a long time to find focus, otherwise the high magnification objective could also hit the slide. If you are having a difficult time to find focus then restart with the lower magnification objective.


The viewer should then be able rotate the nosepiece to higher settings and bring the sample into more and more detail with a minimal amount of refocusing.

Some compound microscopes come with what is called a rack stop. A rack stop prevents the objective lenses from being lowered into the slide.

However, some older microscopes do not have a rack stop, so it is always advisable to check, just in case. Lowering an objective lens into a slide could easily break the slide and damage the sample.

In order to move your microscope safely, one hand should be under its base for support and the other at its arm. Be sure to only switch off the microscope when the dimmer is set to the lowest intensity and always turn off the lamp before moving the microscope.

So now you know how to use and adjust a compound microscope. Well done. Happy Viewing!

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