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14 : Choosing the Right Microscope Irrespective of

price, toy shops do tend to sell toys! What to Look For

So what should a beekeeper look for in a high power microscope? Starting at the top, the high power microscope can have one eyetube (monocular), two eyetubes (binocular) or even three eyetubes (trinocular – two for you and one for a camera). The choice of head will significantly affect the price. Binocular and trinocular microscopes are much more expensive than monocular because of the prisms that they have and the skill needed to align them correctly at manufacture. However, the monocular image is not inferior, but if the microscope is used a lot, binocular is certainly more comfortable (and more impressive!)

Moving down the microscope

it is the objectives that really matter as these produce the resolution of the detail that you want to see. These should always have the Royal Microscopical Society (RMS) standard screw thread (again beware the toys) and be at least achromatic in lens quality. All RMS objectives will be this unless they are superior quality when they may be marked with the word PLAN and may show the infinity symbol. In general terms, the more the microscope costs the better the quality of the objectives and the better the image quality. However, for the needs of beekeepers the more basic achromatic objectives are fine. It is important to ensure that the microscope has a x100 oil immersion objective which would be used to see bacteria. This is a requirement for the BBKA microscopy examination. Next the stage. High power microscopes reverse the image

so moving the slide around the stage by hand is quite difficult. The stage should be mechanical with gear controls to move the slide from side to side and backwards/forwards. These controls are often on the same stem and are called coaxial. There will be a spring loaded clamp to hold the slide in place. Beneath the stage should be a condenser lens to focus the lighting onto the slide. The condenser should be able to focus up and down and have an iris diaphragm and filter carrier. Just as important as the objectives is the light system. There are still a few student microscopes with a mirror light system available; while adequate, they are not very convenient. Tungsten or, more commonly, LED lighting will be built into the bottom of the microscope. This should have brightness control as the amount of light needed for a

x100 objective is much more than a x4 objective.


So the check list for the beekeeper is: • monocular, binocular or trinocular head depending on budget

• at least achromatic objectives • mechanical stage • coarse and fine focus control • focusing condenser with iris • brightness controlled lighting • magnifications x40, x100, x400 and x1000.

To obtain that specification does not have to be expensive (Figure 2). Appropriate microscopes start at around £100 (as do inappropriate ones!).

When properly focused the objectives of high power microscopes need to be within 1 mm of the slide (at x400). It is impossible therefore to dissect or manipulate a bee in this sort

Figure 3

Figure 5 Figure 4

August 2013 Vol 95 No 8

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