A Practical Guide to Choosing Microscopes
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Choosing the right microscope
Nature offers some amazing sights to see! It provides remarkable things to observe such as birds, plants and animals, all of which occupy a special place in our view of the world around us. If we happen to be lucky and the sky is clear, we will see a brilliant blue sky with our shining neighbourhood star, or a starry vista that captures a soaring imagination.
Now, look down! Look closer and you’ll see a plant cell that is a marvel of biochemistry or a bug’s leg that is startling in its mechanical efficiency. Hear a universe seems to exist in a single drop of pond water, or a rock’s crystalline sparkle that can challenge any starry vista!
This visual frontier is brought to you by Microscopes!
So you’ve decided you want to buy a microscope! This is where the critical question comes in: what do you want to see with it?
All microscopes provide magnification, enough to see anything from the fine details on a coin to the structures of a plant cell. But not all microscopes are made for the same purpose, and it is important to decide what the primary interest is before purchasing a microscope. What you want to see is going to determine the degree of magnification, or rather, how much ‘bigger’ one wants to make things appear.
– Inspection, stereo or (gulp!) dissecting microscopes: These are used for low power magnifications of generally 20X (times) to about 40X (times). These microscopes are for things like inspecting fine detail in coins or electronics, looking at entire samples like insects or flowers and, of course, getting in close to a biological dissection. They frequently have two eyepieces, but that is not always the case. Microscopes may come in a variety of sizes from huge table top models, with optics tied into video systems, to small simple units that one can take out into the field.
– Biological microscopes: Biological microscopes have higher power than Inspection microscopes and can easily go up to 1,000X (times) magnification. This gets down to the small scale structures such as parts of an insect, cells in our blood, and creatures swimming in a pond or puddle of water. To see these life forms requires either the purchase of prepared slides, which are rectangles of glass with samples prepared and mounted, or the preparation of your own slides.
Okay, we’re not going to take apart an actual microscope but there are parts in common between many different types of microscopes that are helpful to know about.
– Eyepiece(s): This is where the image meets the eye. Also, it’s the relationship between this and the objective lens that creates the magnification. The higher the magnification eyepiece, the larger the image appears. Be careful though, there is a point where higher magnification does not mean better results in biological microscopes, and you could lose resolution. This can be assisted with the use of “immersion” objectives where water or a refractive oil is used to assist in the transmission of light.
– Objectives: This is where the light comes in and dictates the quality of your image. On a biological microscope, there are several objectives that range from low to high magnification and depending on the size and magnification of the objective, they could get close with the slide. Some “toy” microscopes use less optically sound acrylic lenses resulting in a poor image. So while a department store microscope might seem a more “low cost” option, chances are it isn’t going to get much use or create a memorable image so we do not recommend them.
– Focus: The focus knob on the side of the microscope allows you to adjust the focus of the image. This is necessary because, not only are the objectives at various distances, but you are also observing an object in three dimensions. So, as you focus the microscope, you will find various parts of the sample coming in and going out of focus successively. It’s amazing the different details that you see this way and makes time at the eyepiece all that much more fascinating!
– Objective turret: On biological microscopes, you change the magnification by rotating your various objectives into line with the optical path of the microscope. Turn the focus and voila! A whole new view!
– Stage: This is where your sample is placed. In the case of slides, two metal clips hold the slide in place, or in the case of inspection microscopes, the bug, coin, mineral or any other larger sample simply sits on the stage. If you want to change the view, you may have to move the sample. Some stages come with adjustment controls that allow you to move it up and down and side to side, or you can move it by hand. Just be cautious and use very fine movements, as one might have a difficult time keeping your sample in view!
– Lighting: Some illumination is always required and the source and direction of that lighting depends on the type of microscope, and the type of sample you’re viewing. Typically with inspection microscopes, it’s from above, and with biological microscopes, the light comes from a mirror or lamp under the sample and through the stage. Other types of microscopy can involve more complicated use of light, including “polarizing” it. But, for most starting microscopes, this is a little further down the road.
– Chassis: The sturdier the better, which is why we recommend a stronger, metal chassis as opposed to the low cost option which generally involves plastic bodies found in “toy” microscopes.
Well, you’ve got a few choices here. As mentioned above, there are some less expensive microscopes that may only cost around $50. But, as the old saying goes, you get what you pay for. A quality, 400X (times) student biological or 40X (times) inspection microscope may average around $150, while a higher end microscope of both types can easily translate into the hundreds of dollars. But the above mentioned units are going to perform, perform well, and do so for a long time!
What can I do with it?
Microscopes are truly an amazing doorway into a world few of us are even aware exists! Inspection microscopes are popular with a variety of hobbyists including coin collectors, who utilizes microscopes to find small details that help identify important aspects to the history, and authenticity of their coins. Mineralogists and prospectors might use one to find trace precious metals in samples from prospecting claims. Biological microscopes allow us to look into the goings-on in a pool of water, structures of plant cells, and to see just what teems at the smaller scales of our living world.
It’s important to have realistic expectations and there are some things you cannot see. Individual molecules and atoms require a lot more magnification, and may require an important discussion with your bank, since this kind of magnification and equipment needed, requires a substantial investment. Vieweing viruses and bacteria with entry level microscopes is difficult. Being extremely small, they may appear as a black dot at the highest magnification, if one sees it at all!
Photography and imaging is possible. This is easily done with a special camera designed to fit right into one of the eyepiece holders that plugs through the USB port in your computer. There are also some specially designed microscopes available from prominent manufacturers that operate entirely through computer interfaces. They work quite well, and offer a chance to share the joy and fascination of what you can see with a wider audience, from close friends, family to the entire classrooms!
So take a look at your options, decide what you want to see and, of course, always seek the advice of experienced experts!
An entire micro world awaits!
The Staff at New Eyes Old Skies