Most of us remember using microscopes when we were in biology class, watching microscopic organisms moving around, bumping into each other.  Although we thrilled to watch the action under the lens, we really didn’t pay much attention to the microscope itself.  If you were to purchase a microscope today you might be surprised to learn that there are several different types of microscopes available depending on your use.<p>The most common microscope is the compound microscope, which is meant for measuring at higher magnifications from 40X up to 100X.   The other type of commonly used microscope is called a stereo or dissecting microscope.  It uses two eyepieces and two paired objectives.  It may use a built in light source from above, below, or none at all. Magnification is usually from 10X to 40X.
Stereoscopic dissecting microscopes have separate optical pathways for each eyepiece.  When viewing your sample you get a three -dimensional view of your specimens at relatively low magnifications.  These microscopes also have a large field and a longer working distance than what you find on compound microscopes.  Whereas compound microscopes are used for looking at slides, dissecting microscopes are meant for viewing larger samples.  
There are two basic types of dissecting microscopes.  One style allows you to read at two fixed magnification settings, such as 10X and 20X or 10X and 40X.  The other style has the capability to magnify at many settings, or “zoom” rather than to be set at two stationary magnification points.   By turning a dial you can literally look at every magnification between two end points, usually 7X and 45X.  This greatly increases your ability to view samples.
Dissecting microscopes can be purchased with or without built-in lighting.  Built-in lighting involves an upper illuminator for reflected light (episcopic) and a lower illuminator for transmitted (diascopic) light.  The most common lighting is by halogen lamps, but you will find a lower fluorescent lamp in some models.  Fluorescent illumination is used for examining heat-sensitive specimens such as in embryo transplant work.  Accessory light can also be added to dissecting microscopes in the form of a ring light, coaxial illuminator or fiber optic light pipes.  Various color filters can be added for specific applications.
You can also vary the stand that your dissecting microscope body sits in, thus changing the working distance.  A typical dissecting microscope has a fixed stand with a rack &#38; pinion for moving the body up and down.  This gives you a smaller working distance in which to work.  You can also purchase your dissecting scope on a boom stand, which greatly increases the space under the scope.  This also allows you to have the microscope stand out of the way when you are working with larger items which may normally interfere with the position of the stand.
Although dissecting microscopes always have at a minimum two eyepieces, you can add a third “eyepiece” or port for a camera system.  There is a wide array of camera systems available, running from digital to video.  Most cameras can be attached to this trinocular port with an adapter, and then linked through a USB port to the software in your computer.  
Whether you are a biologist performing dissections, a technician building or repairing circuit boards, a paleontologist cleaning and examining fossils or a hobbyist who needs to work with your hands on small objects such as rocks &#38; bugs, you will find a dissecting microscope to be a very useful tool.
Dissecting Microscopes