Finding a Place for the Microscope

• Use microscopes on a flat, stable surface. An electrical outlet should be within reach of the microscope's electrical cord for the illuminator, the lamp in the microscope's base that provides the light needed to view the specimen. When plugging or unplugging the microscope, grasp the cord by the plug rather than the cord itself. If necessary, move the microscope to a more appropriate location with one hand under the base and one hand holding the arm of the microscope.
  
  

Setting Up the Microscope

• Once the microscope is in a desired location, rotate the nosepiece -- the part of the microscope where the objective lenses are located -- until the low-power objective lens is above the stage opening. The low-power objective lens is the shortest of the objective lenses, but the objective lenses are also engraved on their side with their power. With the low-power objective lens in place, turn the coarse adjustment knob until the stage and objective lens are as close as possible. The coarse and fine adjustment knobs move the stage in many microscope models; however, some designs move the head of the microscope instead. In either case, the coarse or fine adjustment knobs increase or decrease the distance between the stage and the objective lenses.
  
  

Placing Slides on the Stage

• Place slides on the stage and secure them with stage clips. The stage clips of some microscopes are metal, spring-loaded clips that require the slide to be manually moved to change the view in the microscope. Microscopes that are more expensive often feature a mechanical stage that allows the slide to be moved across the stage, often with the use of two knobs, each for the X- and Y-axis. The stage opening is a hole in the stage that allows light to pass through the stage. The part of the specimen to be viewed in the microscope should be placed over the stage opening.
  
  

Focusing the Eyepieces

• Binocular microscopes feature two eyepieces -- one for each eye. The distance between the eyepieces -- called the interocular distance -- may be widened or narrowed to suit the distance between the observer's eyes. Often, one eyepiece is fixed and the other is telescoping. This means that the eyepieces may be focused to account for differences in the vision between the observer's eyes. Focus the telescoping eyepiece by rotating the eyepiece, making graduations around the eyepiece. Focus the eyepieces by using the coarse adjustment knob to focus the specimen while observing through only the fixed eyepiece. Once the image is clear, observe the specimen using only the telescoping eyepiece, and rotate the eyepiece until the image is clear.
  
  

Adjusting the Light

• The condenser focuses the light from the illuminator onto the specimen while the diaphragm regulates the amount of light reaching the specimen. The diaphragm is often adjusted using a wheel on the stage. Both the condenser and the diaphragm should be set according to the particular magnification, specimen and desired contrast. Generally, the diaphragm is opened to allow more light at high magnification and less light at low magnification; this is due to the smaller field of view at high magnification. If the image in the microscope is too bright or too dim for clear observations, adjusting the iris diaphragm should resolve this issue.
  
  

Changing Magnification

• Increasing the magnification of a specimen simply requires rotating the nosepiece to the next higher objective lens, with the exception of the oil immersion lens, providing maximum magnification. Compound light microscopes are typically designed to be parfocal, meaning the image remains in focus or nearly focus when the objective lenses are rotated to a different magnification. Any focusing done on higher-power objective lenses should be made exclusively with the fine adjustment knob. Using the coarse adjustment knob with higher-power objective lenses can cause the specimen to hit the objective lens, possibly damaging the objective lens, specimen or both. The oil immersion lens requires the use of immersion oil on the specimen. Once a drop of oil is placed on the slide, the oil immersion lens -- the longest of the objective lenses -- is rotated into place so that the lens enters the bubble of oil.