So - you want a splendid holiday microscope? (II)

Finally our bigger holiday microscope equipment looked as shown in the image below:

Trinocular microscope
"BTC BIM135T" and stereo microscope "MBS-10"

As we did already discuss the MBS-10 extensively elsewhere we will concentrate on the entry-level compound microscope sold under the name BTC BIM135T.

Trinocular microscope "BTC BIM135T". Ebay, ca. 400 US $ plus shipping costs. Halogen lamp 12V/20W. Condenser with a Numerical Aperture of 1.25. Iris diaphragm and filter holder. Fourfold objective revolver, fitted with four "semi-plan" achromatic objectives 4x, 10x, 40x and 100x (oil immersion). For tardigrade studies the gap between 10x and 40x is too big, so we decided to add a cheap 20x achromatic objective. 10x wide field eye-pieces. X-Y-stage with coaxial knobs below the stage, condenser knob for condenser height adjustment. Coaxial coarse and fine focus. Photo tube (either 100% visual or visual plus photo). Home-built photo adaptation for a digital mirrorless Sony Nex-5N camera.

There was also a smaller sister model, priced for about 60 US $ less, called "BTC BIM105T". It has no condenser adjustment knob and more modest achromatic objectives (not semi-plan). Overall those prices might still look like a lot of money for most of our readers. But we shouldn't forget that this kind of microscope would have cost about 2,000 US $ in the 1970s.

We were curious whether the optics and mechanics might come close to our older "branded" microsopes as there are many contradictory statements about this topic all over the web, for example:

-- "The best buy will alway be a used microscope from a famous brand!"
-- "I cannot see any differences in practical work!"
-- "Cheap import scrap, not worth discussing!"
-- "Look, I got it even cheaper!"

Lateral view of the "BTC BIM135T" microscope. Double arm stand. High voltage transformer located within the base. Adjustable illumination intensity by means of a wheel. On top, about in the middle of the image: metallic drawtube for change between the visual and the mixed visual-photographic illumination path.

Condenser region of the "BTC BIM135T" microscope. Height adjustable and centering condenser, milled wheel iris, filter holder. Everything fully functional, but not as flawlessly finished and lacquered as in the case of the more expensive microscopes. A lot of plastics but working plastics - no complaints.

So what ???

Basic use, focusing and light are fully functional and all movements are working (no disturbing backlash, no vibration tendency when focusing etc., no light flickering). The image is quite clear, the field of view not luxurious but appropriate and sufficiently flat. Obviously the design is oriented towards the beginner with no special refinements or complications. Just switch the light on, choose the appropriate objective needed, focus - that's it. The visual image impression is flawlessly, not worth further discussion with respect to practical use. The instrument can be used with almost no contraints for water droplet microscopy and even for use with modest incident light, as might become clear from the images below where the incident light is coming from aside:

Incident light photomicrograph of a sea sand sample, taken by means of the "BTC BIM135T" microscope. Anthropogenic particle in the middle of the image, presumably artifical resin with some printwork. IKEA "Jansjö" LED lamp. Image width ca. 1 mm.

Incident light photomicrograph of a sea sand sample, taken by means of the "BTC BIM135T" microscope. Natural scale fragment, mother nature printwork.
IKEA "Jansjö" LED lamp. Image width ca. 1 mm.

Some limitations became apparent when using the microscope for the study of the marine tardigrades. As already mentioned in our last issue the field of view shows an uneven brightness, therefore doesn't look as clean as with our classical microscopes. The so-called "Köhler" illumination as recommended by microscopy priests is not available. As a consequence some light energy is dissipated and the 20W source might appear a little bit too dark in extreme situations. Nevertheless the instrument is quite usable as a holiday microscope. The following photograph might serve as an example to make up your mind:

Marine tardigrade from Croatia. Focus on a front leg with four delicate claws. Photographed by means of the "BTC BIM135T" microscope. Image width ca. 0.1 mm.

Summary: this microscope is by no means a high-end scientific microscope but it is well suited for the beginner, also a more ambitious beginner with budget restraints. It can be used for photography as well but it is not as flexible and not as upgradable as the more expensive systems.

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed.

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