The 4 cm microscope
Of course it is fascinating to dircetly look at the development of life in those "glasshouse"
tardigrades as Ferdinand Richters put it a century ago. In the case of other organisms
it is much more difficult to look inside. We would have to crush some shell or to cut the eggs into slices
in order to get similar insights. Almost no preparation, no fixation, no microtome ...
And when proceeding carefully we can follow the egg develoment until to the moment of hatching.
Detail view of a tardigrade exuvium with eggs by an Echiniscus tardigrade (the tardigrade
has left its egg in the old skin after moulting). The microscope is being focused
on one out of eight eggs. Please note the egg cell walls and the stage of develoment
(called morula stage because it resembles a mulberry), still with identical
cells, before specialization occurs. On top of the image the structure of the
cuticula can be seen. Image width ca. 0.1 mm.
But when there is dust in your benchtop microscope or on your DSLR camera chip
you might still wonder whether all this might be reached also by much cheaper devices, like those ubiquituous Ebay gadgets.
They come with inbuilt light, tiny levels and knobs, thus providing the air of science at its best.
Cheap pocket microscope (Ebay). On the right hand side,
just for comparison a tiny 20fold loupe which has been used in students biology courses a long time ago.
Well, is it just a toy? Simply put, the biology course pocket loupe shows a better performance
but the "pocket microscope" has more functions.
Cheap pocket microscope (Ebay). Dimensions ca. 40 mm x 40 mm x 20 mm. Weight 20g.
Price including postage ca. 5 US$. The (black) eyepiece opening is shown in the (bottom) middle of the image,
the battery cover to the right contains three tiny silver batteries. On top the focus wheel.
Cheap pocket microscope (Ebay). Three position switch on the left side with torch light//OFF//(Raking) microscope light. With the black round button on top pressed you will be able to use UV light.
Now let's have a look at the inside:
Cheap pocket microscope (Ebay).To the right, within the black cylinder there is a two lens optical system
which can be moved up and down by means of the focus wheel. The "eyepiece" opening is just a hole, contains no optics at all.
How about the optical performance? Soberly speaking this instrument should not be called a microscope, it is just a strong loupe.
E.g. you will not be able to resolve the test diatom Triceratium favus for which we would need a - rather modest - numerical aperture of 0.1.
This test diatom structure is easily resolved by most dissecting microscopes like e.g. the Russian MBS-10 which has been reviewed here in depth about a year ago.
The field of view of the "pocket microscope" is able to show an object with a size of 5.5 mm in full view. But, sadly, of this 5.5 mm image width only those two
in the very center appear crisp, the remainder is strongly blurred.
When comparing with the MBS-10 dissecting microscopes' 28x magnification not only the MBS-10 detail resolution is much better but we take profit from a
greatly enlarged field of view as well - by a factor of 20! Moreover, due to the low working distance it is not possible to screen the contents of a petri dish for tardigrades.
On the other hand, in case you should be primarily interested in postage stamps or in a quick view at classical permanent preparations on microscope slides,
the pocket microscope might serve as a tiny helper and come in handy. Overall, in particular when keeping in mind the very modest price, possibly a funny
gadget for casual use but certainly not a tool for our tardigrade studies, sorry.
The next magazine will be devoted to 3rd party recent 3D creations featuring - as you may guess - tardigrades.
© Text, images and video clips by
Martin Mach (firstname.lastname@example.org).
Water Bear web base is a licensed and revised version of
the German language monthly magazine
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