A dual view microscope is an excellent tool for sharing visuals and for teaching.  Essentially, it is a microscope (usually a monocular type) that features a second viewing port.  This vertical port has a two-fold use: one is as a viewing port for another user and another as a port where a digital still camera or video camera may be attached.  Because the second viewing port may also be used by another person, usually an instructor, the dual view microscope is also called the teaching microscope so it is often used in science classes.  This short buying guide will help you choose the right dual view microscope by considering the following important components:

Eyepiece
Older microscopes have a vertical eyepiece that forms a strict 90 degree angle with the base, which make them less flexible when it comes to viewing.  Newer models of dual view microscopes usually come with one vertical eyepiece and one inclined eyepiece.  The vertical eyepiece is often used for attaching a video adapter.  There are also dual view microscope models where the viewing head may be fully rotated 360 degrees, allowing users to reverse position for viewing.

You might want to consider buying a dual view microscope that has a wide field lens in the eyepiece.  This will widen your field of view and allow you to see more, reducing the need to move the specimen slide during viewing.

Lens
Optics is what sets a microscope apart from other types of image enlarging instruments.  In fact, this is the component that makes up a microscope, regardless of what type you’re using.  The better the quality of your optical parts, the better image you will have and the longer your dual view microscope will be useful.  Look for optics that has the DIN or JIS standards, the German and Japanese international standard used for glass objectives, respectively.  A lens system that meets the standard will help you find a replacement in case your objective lens gets damaged or stolen.

Focus
The focus system on a dual view microscope is made up of a coarse focus and a fine focus.  The coarse focus is usually the first knob that is manipulated in order to view a specimen.  For higher magnifications, the fine focus is used.  Try the microscope personally to see how well the focus system works.

Illumination
Light is an important factor in every microscope model.  The clarity of the images viewed through a dual view microscope will depend largely on how effective the illumination feature is.  There are basically two types of light sources used for microscopes – one is with the use of a sub-stage mirror and another with built-in electric illumination.  A mirror-only dual view microscope will be quite cheap to operate but it will significantly limit your viewing options.  A dual view microscope with a built-in electric light bulb, on the other hand, allows more flexible viewing choices.

There are different types of bulbs used with dual view microscopes, each one more beneficial depending on your requirement.  A tungsten bulb, for example, may be cheaper but it is naturally tinted, which may affect the color of the specimen you are viewing.  It can also generate a lot of heat.  Fluorescent bulbs don’t heat up as much and they also provide whiter light similar to natural lighting.  For amateur or student users, a fluorescent-powered microscope will suffice.

However, the dual view microscope has two viewing ports, which might require stronger illumination.  A good choice would be the halogen bulb, which is capable of producing intense white light.  This makes it the preferred light source for many research and medical microscopes.

As an alternative, look for a microscope that has an optional mirror attachment.  In case of power failure or a lack of power source, you can always use a mirror to illuminate your specimen.  Look for a dual view microscope that allows you to easily detach the bulb and attach a new one.  Most of the bulbs that come with dual view microscopes are standardized so they should be easy to replace.

Color
While some microscopes may provide colored images of a specimen, they are often false or inaccurate colors.  Some dual view microscopes are achromatic.  Since lenses in a dual microscope are composed of several glass lenses, there is a chance that the focal plane may not be aligned accurately.  This causes some colors to become invisible and thus unseen and undetected through the eyepiece.  A color-corrected set of lens in a dual view microscope will help you view images of the specimen with more accurate colors.

Furthermore, optical distortion is also minimized, making the center 60% view near perfect.  The outer 40% will have some aberrations but it shouldn’t bother you too much since the natural tendency of the human eye is to focus on the center.  If you prefer a perfect view, buy a 100% aberration-free lens dual view microscope, although be prepared to spend because it is considerably more expensive.

Other considerations
The dual view microscope has numerous parts you will need to consider when buying a unit.  These are the diaphragm, the condenser, filter holder and other mechanical parts such as the stage and slide holders.  Inspect the microscope yourself to see how well the parts work together and if you do get the magnification you wish to achieve.  Be realistic and learn about your instrument’s limitations.  You will pick a better instrument if you understand what it can and cannot do.