The first thing you should ask yourself is, "What do I want to use the microscope for?"  Are you interested in dissecting insects, inspecting leaves or flower petals, looking at a dragonfly wing, inspecting small electronic parts?   Then you want to purchase a stereo microscope.   A stereo microscope is binocular, which means that it has two eyepieces (think of a pair of binoculars).  It is usually of a low power, such as 10x, 20x, 30x, and 40x magnification, and has a large stage (viewing area) to accommodate three-dimensional objects.  No slides are required--the specimen can be placed directly on the stage.   This is often a good choice for small children because it is simple, easy to look through, and allows them to get a closer look at everyday objects.  Some stereoscopes come with a light source which I would recommend.  Look especially for fluorescent lighting which is cool and will not dry out specimens as incandescent lighting can do.   I own a stereoscope without a light source and find that it works very well when used in a sunny location which provides plenty of light for viewing. 

If, however, you are interested in viewing slides of pond life, pollen, skin cells, mold, bacteria, etc. you need a basic compound monocular microscope.   You want to look for a scope that has 4x, 10x, and 40x objectives at the minimum.   You can go one step further (and a few bucks more) and purchase a scope with a 100x oil immersion objective as well.  Let me digress for a moment to explain what these numbers I'm tossing around mean.

The objective lens is the lens mounted on the nosepiece of the microscope--it is the lens closest to the object.  The magnification is typically, as stated above, 4x (4 times), 10x (10 times), and 40X (40 times)--you get the picture.  In addition to the objective lens, a microscope has an eyepiece lens, usually 10x.  To figure the degree of magnication that a scope gives, you must multiply the power of the eyepiece by the power of the objective lens. For example, 10(eyepiece) x 4(objective lens) = 40 total magnification.  Therefore, the typical scope gives you 40x, 100x, 400x, and up to 1000x total magnification.  It's not complicated, but it is an important thing for you to know.

When looking for a monocular student microscope there are several things to consider:

• If you purchase a scope that includes a 100x oil immersion lens (which means that you must use immersion oil for viewing objects with that objective) or if you plan to add a 100x objective at a later date, you should have a fine adjustment control on the microscope.  Some scopes have only a coarse adjustment knob and that usually works OK with lower powers.  But for high power viewing you will need fine tuning ability for satisfactory results.  While a 100x objective lens and other accessories can be added to your scope at a later date, you can not add a fine focus knob.  So, you might want to spend the additional dollars to purchase this feature up front.

• You may want to purchase a mechanical stage along with your microscope.   The mechanical stage mounts on the platform of the scope and allows for much easier and more precise adjustments of the slide.  While this is not a necessary feature, it is convenient to have especially if you plan on viewing specimens at high power where a slight nudge of the finger could move your specimen right out of the field of view.
   
• Look for a scope with a good light source.  I do not recommend microscopes with mirror illumination if you are serious about using the scope.  A good light source--preferably cool fluorescent--is a must for successful use of your scope.
  
• Most scopes come with a built in diaphragm which allows you to control the amount of light which hits the specimen.  Some scopes have disk diaphragms which operate as a wheel of different sized apertures that you rotate to adjust the light.   Much superior to the disk diaphragm is the iris diaphragm which allows for an infinite number of lighting configurations.  Look for a scope that specifies that it has an iris diaphragm.  Even if it costs a little more, it's worth the extra money.
  
• Most scopes also come with a condenser that controls how the light actually hits the specimen.  If you plan on viewing at high powers, you should look for a moveable condenser which allows you adjust the light most effectively.

The last thing to consider when purchasing any scope is the optics.   It goes without saying that for optimal viewing you must have quality glass optics.   There are a few terms you will run across in your search for a high quality optical instrument:

Achromatic Lenses:  When lenses are labeled as "achromatic" this means that they have been color corrected so that they will show true specimen color.  If a lens were not achromatic, you might not be able to view all colors.  Achromatic also refers to how much of the lens is focused and aberration-free.  In an achromatic lens, 60% of the center of the lens surface is guaranteed to be focused and without aberrations or flaws.

Plan Objectives:  Lenses that are 100% focused and without aberrations are called plan objectives.  Scopes with plan objectives are usually used in the laboratory or medical fields as these type of lenses are very expensive.  Our Revelation 2000 and Revelation 1000 microscopes both are equipped with plan objectives.

Semi-Plan Objectives:  Also available are semi-plan objectives which are focused and aberration-free over 80% of the lens surface.  Again, these scopes are more expensive and are usually reserved for the serious hobbyists or medical or lab professionals.  Lab Essentials' Revelation III microscope is available with semi-plan objectives.

One more feature to look for regarding optics is widefield eyepieces.   Widefield eyepieces  broaden your field of view while looking into the eyepiece and are easier to look through, especially for young children.

Purchasing a microscope can be confusing, so take your time.  And don't be afraid to ask questions.  At Lab Essentials we will be more than happy to help you in any way we can. Remember the old cliche--the only dumb questions are the ones you don't ask.  Everyone has to start somewhere in their pursuit of knowledge and new experiences. 

We wish you many years of happy microscopy!

The Staff at--
Lab Essentials.com
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