Choosing a microscope

What kind of microscope to get for schoolchildren? Here are some tips from those of us at the Society who have had some experience in schools outreach:

• Conventional compound light microscopes (the ones you look at slides with) can be limited for young children because you are restricted to prepared slides or transparent samples and therefore can be limited at this age. We like stereomicroscopes as they use two slightly different views of a sample to generate a 3D image. They also have a large depth of field meaning that they are easy to focus and can focus on a huge range of objects no matter what the size or transparency. They also tend to use lower power objectives (up to x10 or x20 magnification maximum) so that children can relate what they see down the microscope to the object they are examining. Finally, unlike in compound microscopes, stereomicroscopes generate images which are the ‘right way up’ making interpretation and moving the sample much easier for young children.
• We don’t mind whether they are mono- or binocular. Some people find young children struggle to focus down binocular eyepieces as their eyes are not far enough apart yet to use both eyepieces. If they can use two eyepieces they will get a really good 3D effect using a stereomicroscope.
• Some children focus on the microscope stage or look at their own eyelashes - it’s important to look down too to check they are in the right ballpark or use a camera with the interactive whiteboard to give an idea of what they should be seeing.
• Sometimes microscopes come packaged with the optics moved right down to the base of the stand to save space. In this case you will need to use the screw to loosen the optics and move them to approx half way up the stand to allow you to easily focus most samples. This may need to be adjusted for very large or very flat samples. If you find you are getting close to focus, but can’t get the object quite into focus, you have probably run out of the range of movement of the focussing knob and will need to adjust the position of the optics on the stand. Ideally you would ensure each microscope can be focused before a lesson begins.
• We find that the optics need to be good and at a low magnification or children will struggle to relate what they see to the item they are examining.
• A decent light source helps, but it is difficult to run a class with wires trailing everywhere so we recommend microscopes with LED light sources (which don’t get hot and have a long battery life) or alternatively get a second child to hold an LED torch as the light source.
• Our Loan Box contains a stereomicroscope with built in LED light source which does not get hot, has a long battery life and does not require the use of mains electricity, so no trailing wires. We are currently looking at a range of entry level microscopes and will provide further information here shortly.
• Cameras can be notoriously difficult: they often come with complicated software and need to have drivers installed. The one we supply in our Loan Box is the easiest we have found to use. However, it is possible to take perfectly reasonable pictures using a normal digital camera. Just hold it to the eyepiece (ensure the sample is well lit and in focus) and click. The resulting image will be a circular, with distortion at the edge but by cropping the edges off you can get a really nice image. Here are some I took with my own basic digital camera and a very old, but optically great, microscope:

Original image of coffee granule	Image of coffee granule cropped and enlarged
Original image of sand	Image of sand cropped and enlarged
Original image of poppy seed	Image of poppy seed cropped and enlarged

• Finally, microscopes with built in digital cameras can be purchased. In our experience the cameras in these systems tend to become obsolete quickly. We would recommend using your own digital camera as above, or buying an eyepiece camera which works very well. We are currently looking at a range of these and will add information to the site shortly.