Improving a Tasco 1200x mini microscope

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Experienced forum member apochronaut mentioned improving a Tasco 1200x mini microscope over from another thread. I will quote him in this post and ask / discuss in my next post:

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One other option would be to refit the fairly common Tasco( other badges too) 1200X body with better objectives. In it's natural state it carried 3 non achromat and one low N.A. achromat with a 16mm mount. That microscope can be had for under 50.00, is all metal and sports a good coarse AND fine focus, in stage condenser and disc diaphragm and can take one of those miniature 20.00 mechanical slide carriers( mounts with 1 thumbscrew). ..........

Two AA batteries power a penlight bulb, which can be replaced with an led alternative for 2.00 on the Tasco. The disc diaphragm needs to have N.D. filters glued over the ports with an led, otherwise those penlight leds are blinding. The 16mm to 11mm objective adapters for the original low N.A. objectives could be used to take achromat 11mm objectives, similar to those used on the Tasco Student above. Edmund and others have sold such objectives in mag. of 5, 10, 20, 30 and 40X. With a 40X .65 and a 15X eyepiece a respectable 600X could be realized but with the original 8X W.F. an excellent 320X and maybe 480X could be.

I could even see the possibility of adapting the nosepiece to take short R.M.S. objectives, sacrificing a bit of magnification for the potential to go whole hog on the N.A. up to about ,80 or so.

One advantage of the cast bodies on those older Japanese hobby microscopes is that they are fairly light and they all had a threaded hole in the bottom of the horseshoe casting, so they could be secured in their wooden cabinet with a screw. Any I have seen are 12-24 or 1/4-20, since Japan was encouraged during the American occupation to foresake their metric leanings and go over to inch threads. Many of those older cast bodies will fit right on to a camera tripod as a field support or can easily be adapted to one by upping the thread to 1/4-20 or 3/8-16, whichever one needs.. Kind of handy. They all weigh less than 4 lbs., with most of the likely candidates in the 2 lb. range. The Tasco 1200X with fine focus, modified as above is just under 4 lbs. : 4 objectives, mechanical stage, lower N.A. condenser, disc diaphragm, built in illuminator, coarse and fine focus. They are all under 10" in height, so very compact.

The one drawback of any of them is the eyepieces. Most eyepieces fitted to them are quite narrow field Huygens types. In a few cases wider field designs were used, likely Kellners. To complicate matters, there are several different eyepiece tube diameters. Fortunately, the better body candidates : The Tasco Student and the 1200X with fine focus came with W.F. eyepieces, so they are pretty good but others could receive a wider field eyepiece . Under no circumstances think of trying to use a zoom version of any of them unless the field of view diesn't matter. Zoom superceded the 3 separate eyepieces on that 1200X body in later years. The zoom mechanism restricts the field and the lens system easily images dust and debris.

One of those could be made into a good light 300 to possibly 600X field microscope for no more than 100.00 .

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apochronaut, please kindly advise me:

Is there an even wider filed eyepiece than its 8x WF that I can easily put on the Tasco 1200x?

Is there a good third party 20x -40x obejctive that I can easily put on the Tasco 1200x?

My copy of the Tasco seems to be highly similar to that of apochronaut, if not identical. My experience with it echoes his.

Mine came with 8x "wild field" eyepiece. However, for my eyes with strong prescription glasses (which are very picky and particular with eyepiece), even that eyepiece is barely wide enough. It is close to good enough, though still slightly lacking for my eyes. A wider field eyepeice would be highly desirable.

My copy came with unusable 40x and 60x objectives. 60x objective appears to be in good shape to my eyes, but can barely produce any image (I suspect its NA / resolution is not anywhere enough and working distance is non-existent). 40x has color dye invasion and image quality is very very poor.

My copy has metal corse and fine focus that seem to work fine. In my hands, with a replaced 40x eyepiece + 8x eyepeice, I feel that I don't need the fine focus. The fine focus drive's division seems too small, such that under 320x total magnification, racking the entire fine focus course did not change focus much (though my quick-and-dirty test subject might not be optimal, as it is only a printed black dot on a microscope slide without cover slip).

Again, under 320x total magnification, I personally prefer to use slide clips and my fingers to move slides, rather than using the $20 Amscope slide holder that apochronaut mentioned previously. It fits, but to view the entire cover slip (especially the entire Y axis), a shortened non-standard slide has to be adapted to my Amscope slide holder. I don't have the (rare) Tasco slide holder, so I don't know if it can work with standard slides.

As a replacement 40x objective, I took it from a "My First Lab Duo-scope Microscope". I took off its top thread and directly glued it onto the empty objective slot using expoxy putty. I was lucky: the glued objective is pretty close to parfocal with the 5x and 12x Tasco objectives and produced a decent image. I knew that 40x objective is a decent one, because I had tested with darkfield diatoms before, using a full-sized condenser. It may not have NA 0.65, but still provides decent imagge qulity.

I would like to add a 20x-40x objective to the Tasco, if that can be done easily.

SInce the Tasco has a single lens condenser (which I am guessing provides NA of no more than NA 0.6), low NA darkfield and oblique illumination can be done to enhance imaging. I like this feature very much.

At a size of 10 x 3.5 x 5 inches and 49 ounce, the Tasco 1200x is quite portable, though not pocketable.

Many pocketable microscopes may not be comfortable to use for over 15 minutes though. If I have to carry a miniature tripod to provide comfortale use, then the size and weight benefits of pocketable scopes become obvious.

[apochronaut]

The 1200X with fine focus was made by Carton Optical and by the time they started using the zoom eyepiece the castings were thinner and the overall build of the stand started to decline, although it was lighter. Selsi had grey ones and it was lighter overall with poorer optics.
The 1200X was the top of the line of the mini objective models. All objectives used in them were chip lens objectives , with single element low magnification lenses stacked in the barrel in order to obtain the required magnification..They are not achromatic but the chromatism is not too bad.. Only the 60X objective used in the 1200X model was an achromat. In fact , when the objectives are in good shape, the 60X is a much more useful objective than the 40X, with better contrast and resolution. It is too bad yours is fouled.
A number of companies had Carton and others make better hobby microscopes with small achromats. Some of these can work in the Tasco nosepiece. There were also other small bore W.F. eyepieces. The Tasco eyepiece is quite a wide diameter, very close to R.M.S. but about a mm smaller, however yes; the field is restrictive
I will check on some measurements and find some options.
New Edmund sub R.M.S. objectives can be made to work but they are expensive. Best to find them on a cheap existing stand.

[apochronaut]

Have a look at this. I already confirmed with the seller that the thread is 15.88mm, so will fit the Tasco.
https://www.ebay.ca/itm/Edmund-Scientif ... ect=mobile

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Have a look at this. I already confirmed with the seller that the thread is 15.88mm, so will fit the Tasco.
https://www.ebay.ca/itm/Edmund-Scientif ... ect=mobile

Thank you very much, apochonaut.

Indeed thread diameter is 15.88mm.

I prefer to have a 20x objective and a possibly a 60x objective. A 50x objective is too close to a 40x objective.

I have checked everything again. My adapted 40x objective is actually pretty good; IQ is better than all 4 of my Tasco objectives.

I managed to take apart the original dye-invaded 40x Tasco objective, removed dye and put all 3 (2 singlets and 1 doublet) lenses back. Contrast is still very poor. Maybe I failed to put lenses back in correct direction / arrangement or my finger oil contaminated the lenses.

I also looked through my original Tasco 60x objective. It actually produced an image but contrast was ever poorer than the 40x. I then took it apart. Nothing looked wrong and everything looked like they were original / clean and never tampered with. So I put back 3 lenses (2 singlets and 1 doublet). Nothing improved. Again I might have messed up something; so I am not positive on that.

Is it possible that there were multiple versions of the Tasco 60x objectives (with my being poorer version)? Or maybe mine was made on Friday 4:30PM?

I had fun but learned something today: with my skill level, I should never disassemble a high power objective again.

[apochronaut]

The microscope sold for 30.00 here in 1965 after being shipped from Japan to Florida, then to Canada, then to the retail distribition, then to the store. There was probably duty at two borders. All of the 60X objectives I have looked through( about 6 were the same but later they may have cheapened them. On the microscopes that came with 3 eyepieces the base was cast iron, hence the extra weight. I have seen one badged Selsi, with zoom and it was all aluminum with cheaper objectives.
The 60X I have looked through were not too bad, working at about .50 or so, thus with the 8X eyepiece the 480X is pretty good. They seem to require very accurate illumination to get the contrast up and reduce the image shatter that occurs with a misaligned mirror. I haven't found led to be too bad if aligned but filtered incandescent is best. I would definitely use those 60X objectives in the field but not the 40X. They realized that they needed a better design for the 60X and it is in all ways better than the 40X.
They knew that the 15X and 20X eyepieces were fluff but they engineered the optics to resolve acceptably with the 8X. It will be hard to find a 21mm W.F. eyepiece better than the one supplied. They've got it right on the edge of possibility with a 2 lens eyepiece and I don't think there would be too many 3 element ones of that size. Probably zero.. That is the only 21mm eyepiece tube I have seen. Perhaps you could adapt a 23mm tube?
The objectives are actually 11mm threaded into a 16mm adapting collar. Those little mini Japanese objectives seem to all be either 10 or 11mm, then threaded into an adapter of between 13 and 16mm.
Edmund sold a series of better grade student microscopes with achromats in them. The basic model had a 10X , 20X and 40X objectives of pretty good achromatic correction. They are 11mm into a 13mm collar but fit the Tasco. Also seen as a Monilux. The later all cast aluminum model is only 2 lb. 3oz. but earlier ones had a cast iron base. Coarse focus only.
Here is an earlier one. The objectives don't look like the later ones but if you can get a pic. of the front of them, they all should have a fairly wide planar front lens. If it is a little hole, then they may not be achromatic. The measure could have changed too. Must be 16mm collar or 11mm barrel.
There is a possibility that some brand of Japanese R.M.S. objective( or other) threaded the barrel into an R.M.S. collar. Kyowa did but they reversed the threads : female barrel/male collar. Someone may have threaded a 16mm barrel into an R.M.S. collar.

Edmund microscope. https://www.ebay.ca/itm/Microscope-Edmu ... ect=mobile.

This Tasco student microscope has better optics yet but they are 10mm barrels into a 15mm collar. Maybe plumbing tape would take up the slack, or glue them in?
The instrument itself is excellent : small very sturdy. Around 2 3/4 lbs. The one in the link just has a loose nosepiece.
The eyepiece says 10X W.F. and is probably a Kellner because despite the tube being only 19mm the field is the same as the Tasco 8X in a 21mm tube. You probably could adapt a sleeve for it to work in the fine focus body but at 300X it isn't necessary to have fine focus, so the Tasco Student body is probably the best place for those objectives. The similar models with higher magnification may be later production and from China despite the similar look. They might be R.M.S. You have to look for the inspection certificate from Japan on the door. The one I have is from 1966.

https://www.ebay.ca/itm/Vintage-Tasco-S ... ect=mobile