How to Use a Microscope

Take the Stage

The microscope stage is the small platform on which specimens and slides are placed or secured for observation. Microscope stages can be either stationary or vertically adjustable, e.g. with a stationary objective lens. But more significant is the double-axis controllable stage positioning of high-power microscopes. That's because when viewing at a higher magnification, keeping the slide or specimen completely still is essential; even a slight movement could take the slide completely out of view. To avoid this, ensure that the specimen is positioned above the light source and held firmly in place with slide holders.

But before you start examining slides, it's best to gain some familiarity with your microscope's focus knobs.

Get Focused To acclimate your eye to using a microscope, start with a specimen that features easily recognizable patterns, such as a dollar bill or a business card with a raised font. For such relatively large "specimens," a microscope with a low-power objective lens will be needed. Before you start squinting through the eyepiece, get acquainted with the knobs for coarse-tuning and fine-tuning. Go slow with the coarse tuning: adjusting too quickly may cause an unwanted collision with the stage, which could cause damage to the lens. Once you're familiar with how tuning works, look through the eyepiece and see how adjusting the coarse focus knob or fine focus knob affects the image.

Working Distance

Working distance refers to how far a microscope's stage, arm, or tube can move vertically for focusing. That distance, along with the working distance of the objective, determines how large, i.e. thick, a given specimen can be. Lower-powered microscopes, e.g. a stereo microscope, have a much greater working distance, which allows the viewer to examine larger objects such as coins or stamps. A narrower depth of field is necessary when looking through high-powered microscopes.

A typical working distance for stereo microscopes is 50mm; for high-powered oil immersion objectives, the working distance may be as small as 0.1mm. The working distance of an objective will decrease in proportion to the increase in resolution, magnification, or numerical aperture.