Friday, April 12, 2013

Your child's first microscope (or a gift for your grade-school teacher)

This post can be summarized thus: Buy a used dissecting scope on Ebay.

Parents and grandparents love to purchase microscopes for their favorite children.  My parents did; and I did the same for my kids.  Perhaps we are motivated by the idea that we can stimulate interest in science?  Personally I like the motivation but not the potential result of a poor purchase choice.

Toy manufacturers market cheap plastic compound microscopes with poorly mounted optics and underpowered battery-operated light sources.  I think that these toys are truly junk and likely to lead to frustration rather than deep fascination for science.

Looking past the quality issue, the more fundamental issue is the choice of microscope type.  Compound microscopes magnify 100 or more times and are great for looking at the scales on a fly's wing mounted on a glass slide.  Light shines through the specimen and the more you magnify, the more light you need to see anything.  The maximum magnification on some of these scopes is often non functional as a result.  Only thin specimens or slices of specimens through which light can be transmitted will work.  I suspect that many kids starting out would rather look at the whole fly.  And by the way, could we skip the whole glass slide part?

This is where dissecting (AKA stereo or stereoscopic) microscopes come in.  A child or college professor can pop an insect, coin, or fossil onto a dish or piece of paper under a dissecting scope without slide mounting and get a good look in seconds.  Because they typically magnify in the 10 to 40 X range, you see the whole organism and can get by with room light or with a flashlight.  Chunky specimens like fingers and coins are fine because stereo scopes make use of reflected light.  My five-year-old daughter had no difficulty examining insects, twigs, and rocks using an old dissecting scope and natural light on a picnic table at a camp out last spring.  In fact she spend close to 2 hours hauling her spectacular finds out from rotting logs and proudly sharing the view with anyone and everyone near by.

Other big advantages of dissecting scopes include large depth of focus and deep working distance.  In other words, more parts of thick specimens will be in focus at one time than under a compound scope; and there is more room to place specimens between the lenses and the stage.  And I did mean 'lenses'; there are two aimed at slightly different angles resulting in a 3D view of your specimens.

So what might you purchase?  Some very nice stereo microscopes made in the 50s, 60s, and 70s by American Optical were in use in schools and colleges across the country and in many cases still are.  Many have found their way into the used market and are plentiful on Ebay.  Search for "American Optical forty" (photographed above) and expect to pay between $50 and $150.  My search revealed 8 today, and the number is low because I purchased 8 last week for an outreach program.  These scopes are heavy, stable, and durable.  They come with built-in lights and two levels of magnification.

Tweezers from your nearest pharmacy make great forceps (and with your new scope you can more readily and gently remove splinters).  Plastic lids from jars are a great substitute for Petri dishes and will protect your microscope from scratches.  Medicine droppers are worth having and usually come 2 on a card for under $4.  Need a plankton net?  Use a nylon stocking and a coat hanger.  Drop a baby food jar down into the foot and secure it with rubber bands around the neck.

If you find that your budding scientist is spending a lot of time on the microscope and getting serious about things, you could consider trading up......