Nikon H field Microscope [Archive] - REMOTE, AUSTERE, WILDERNESS & THIRD WORLD MEDICINE

DrBaboon

11-28-05, 00:28

It looks like a really nice microscope.

I did some reading on the microscope hobbyist site you referenced - and saw some mentions of other portable microscopes.

The Nikon H still looks like the best in terms of capability (as long as you can get objectives for oil and for high power - there is also apparently a long working length high power objective - see discussion on hemacytometer below). It looks as if some people have certain objectives, and other people bought theirs with other objectives.

I thought I'd mention some currently manufactured/currently available portables:

http://www.opticsplanet.net/micpormic.html certainly not cheaper than a used Nikon H, and it's limited to 400x, so you're not going to do well reading medical specimens like stains. I get the idea that it might be made in one of the former Soviet factories - there is a US company distributing it, and there is additional information on their site:

http://www.omextech.com/micromet.htm

The Omex site doesn't talk much about it, but they show a 20x widefield eyepiece at the bottom of the page. If that's accurate/available, it would get you to 800x, and you'd be able to do decent high power microscopy, but still not be able to do oil immersion.

That also made me wonder if one of the following strategies was possible: 1) Omex solicits people asking for custom work - could they provide an oil immersion objective as an option? 2) How standard or atypical are the objectives? Could a 3rd party oil objective be installed in place of the lowest power objective? Or could an intrepid & determined individual machine the metal tube of a 3rd party objective to allow it to be installed on this scope?

I mean - all microscope work had to start with people and ideas, craftsmanship, etc.

http://www.microscopestore.com/browse.asp?c=128 The Swift portable microscope looks pretty reasonable, too. It's quite a bit less expensive - I'd look at the brightfield model.

Phase Contrast has its uses, but most "usual" clinical stuff doesn't require phase capability. It'd be more handy for research, or tissue culture work - and I suppose there might be some Austere reasons to consider tissue culture, but that seems pretty ambitious and not too likely.

Note the Swift is also limited to 400x "out of the box." Mel Sobel apparently has an aftermarket 20x eyepiece for it:

http://www.microscopestore.com/info/swift_accessories.asp

Scroll down to FM A739. That will get you to 800x, which is getting there, but you still really need an oil immersion objective.

My questions end up being the same as on the Omex instrument - can a Swift or other oil objective be installed, or can something be machined to work?

FWIW - as nice as the Nikon H looks, it apparently has clips on the stage, and does not have a mechanical stage. I don't know if you can modify and install a mechanical stage on it. Keep in mind that it's one thing to inspect a specimen, and another thing to be systematic in scanning a slide (such as on many smears, or looking at the grid of a hemacytometer). A mechanical stage is really almost essential for that kind of clinical work.

AFAIK - the Omex scope does not have a mechanical stage available, either, so the same question applies about whether one can be made to work on it.

While the Swift portable scope does not have a mechanical stage "out of the box," it appears as if one is available for $207 under accessories.

If someone were really interested in using phase contrast, it looks as if the optics can be purchased for the Swift, and if you only got the 10x phase eyepiece and 40x phase objective, you could add that to the least costly base model that only does brightfield "out of the box" -- which would be less expensive than getting a phase capable microscope with all phase objectives, but no brightfield capability.

Even with lenses that are set up for working distances involved in this kind of inverted microscopy, keep in mind that you're looking at the underside of the slide - not from the top as you would be doing with a conventional microscope. That might not matter much with simple/regular slides.

I did notice people talking about using a different objective on the Nikon H for hanging drop preparations (the special slide would increase the working distance, hence the need for a different objective.

There are clinical uses of hanging drop preps, but they aren't that common or essential (probably the most common reason for hanging drop preps is to look for Trichomonas - if you're lucky, you may see it with other preps, though it's preferable to make a hanging drop). The reason I think objective working length matters for us, is that a hemacytometer will exagerate the problems that you encounter with a hanging drop slide/coverslip. IOW - it may very well create a bigger problem for these inverted microscopes - I don't know if that's within the range of what can be accomodated.

Let me re-phrase that -- the considerable thickness of a hemacytometer will put the specimen chamber pretty high off the stage. On a conventional microscope, you'd simply back off and raise the optics accordingly, and end up with the focal plane at the level of the specimen chamber.

On an inverted microscope, you have to bring the objective "up" much closer to the bottom of the hemacytometer. It's possible that you'll hit the hemacytometer before getting into focus, or that there will be insufficient movement to get into focus even if you don't run into the underside of the hemacytometer.

Normally, in a full-featured inverted microscope (non-portable), you are looking at a coverslip with a cell culture adhering to it, which is on the bottom of a petri dish full of media - or some similar arrangement. IOW - you end up focusing on cells stuck to an object on the very bottom of the dish. You're not trying to focus on the top surface of the watery media in the dish, which is far above the stage.

I'm not sure you could get a hemacytometer to work on a full-featured inverted microcope - maybe you can - I don't know - I haven't tried. But I wouldn't want to assume you could do so without checking.

A portable microscope is more limited in movement and focus, so my suspicion is that it would be more likely to be impacted by these constraints.

I like this portable microscope idea. Hopefully there are some members who have experience with these kinds of portables.