Wanted AO 20 compatible pieces

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Joined: Tue Aug 28, 2018 11:03 pm

Wanted AO 20 compatible pieces

#1 Post by mnmyco » Sat Sep 14, 2019 5:27 am


I recently changed jobs and am paid significantly more. Even better, I was given an AO 20 when I left. It needs nee prisms in the trinocular, has all the standard filters, came with the 1240 phase condenser with 1242 top lens (sadly missing bottom lens for bright field), the transformer, and somewhere I have the lamp itself. Oddly, the objectives on it were not phase. The condenser has the phase rings.

I am looking for:
  • the condenser lens for bright field OBTAINED
  • new trinocular or prisms for it (older trinocular)
  • the aperture viewer OBTAINED
  • polarizing equipment
  • good phase objectives
  • an objective of high NA above 40x and less than 70x
  • good dark field condenser
  • a new lamp and cord, still cannot find the original, but I do have the transformer
  • the trinocular tube for the camera/whatever-else head
  • 5 position nose piece would be nice, but did they even make those? Also, is it a pain to switch out nose pieces on an AO? Never done it before and it is the part that moves
There may be more and I am not looking to buy all at once. My new job pays about 1.5x my old job, but I am still not rich enough to buy it all my in one go. I want to buy or make filters for all the different lighting techniques and colors. Opinoins, should I buy a good condenser with a filter holder as well as my phase 1240 condenser or has anyone done the math for the filter space already provided in the base?

Is it even worth trying to find the pieces to go DIC with it?

Also, I would be very interested in knowing any equipment that is compatible (regardless the brand) with very little to zero modifications needed.


Last edited by mnmyco on Wed Sep 18, 2019 7:54 am, edited 2 times in total.

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Re: Wanted AO 20 compatible pieces

#2 Post by apochronaut » Tue Sep 17, 2019 3:37 pm

Some of these are pretty hard to find. The DIC stuff may be out there but in my experience it usually shows up in the drawers of former dealers and seldom as a complete lot. Recently, there was a complete vertical DIC set, that came out of a storage container.

The # 1242 condenser, used for phase is perfectly usable as a dry ,high N.A. BF condenser. It's a pretty sophisticated condenser . Although no data shows up for it. It's .90 or .95. If you want an abbe or abbe aspheric oil 1.25 condenser that you can thread into that condenser body, I have one.

It would be a labour of love to replace the mirrors in that trinocular. Could be done. Trinoculars are available but I guess their internal integrity would need to be verified by the seller.

Aperture viewer? I guess you mean the bertrand lens version with the flip in flip out prism? I have one of those too.
Polarizing equipment is hard to find. It is out there but usually still attached to systems. Occasionally you see an individual strain free objective or condenser, so I would be inclined to keep looking and pick up what you can, when you can. There are some after market rotaing polarizers to fit over the illuminator window.

Phase objectives , show up on occasion. Same protocol as for the pol stuff.

There are only 4 higher N.A. objectives that fit the bill of your description.
1) cat.# 1303 63X .80 SPL achromat. This was designed at Reichert Austria for their 34mm parfocal microscopes which mostly used AO objectives redesigned with spring noses and different barrels. The design was reviewed and approved by AO for inclusion into their objective lineup in Sept. 1982. Not a whole lot of them were sold. Occasionally, you see one in North America but there are more of them in Europe. Unfortunately, sometimes at very high prices. The European version and the North American version are identical, even inclusive of the spring loaded nose.
https://www.ebay.at/itm/Reichert-Jung-M ... Swr~lYrKJg
2) cat.# 1016 50X .80 oil immersion planachro w./ iris. A nicely compatible objective with the 100X 1.25 oil immersion iris equipped # 1014. For DF they work as a nice team, since it always nice to be able to back out of a 100X oil objective to another oil objective, in order to get a wider view.
3) cat.# 1026 50X .85 oil immersion achromat w./iris. An older version of the above. I actually prefer it.
4) cat.# 1029 . This cat. # shows up very briefly in the mid to late 60's, as the first such objective offered for the new infinity corrected lineup. It seems identical to the above , minus the iris and the cat.# later shows up as a 100X 1.25 N.A. oil planachro, after the 50X was discontinued and replaced by the 1026. I have never seen one.
5) Additionally, they made two 40X apos and a 40X .85 achromat. These have the resolution to carry 15X cat.# 184 eyepieces with grace and yield 600X magnification , dry. The original apochromat was a 40X .85 with a correction collar. It had no cat.# that I can find and is very rare. Physically, it looks like the last incarnation of the 160mm 43X .95 apochromat with the brushed chrome barrel but it is clearly marked infinity. It's production was short lived. In the 80's they released the cat.# 1809 40X .85 advanced achromat. Also uncommon. The most common was the # 1323 40X .80 planapo without a correction collar.

DF condensers for the series 10/20 are quite common. There is almost always one on ebay for sale. The common one is the 214F but there were actually 3 types. The 218F is self illuminated and the K2172 is toric, so works down to 10X . All are excellent cardioid oil condensers. You will need either a #1079 100X 1.25 achromat fitted with a funnel stop, a # 1027 100X 1.25 achromat w./iris or a #1014 100X 1.25 w./iris. to get high resolution DF with any of them .
https://www.ebay.com/itm/AO-Series-10-D ... SwCahc3Kyj

As far as compatible equipment from other manufacturers, that would be a complete accident and discoverable only by chance outside of the AO-Reichert-Leica family of microscopes. The Reichert-Leica branch fed off of the AO introduction of infinity, so there was a line of Reichert Austria microscopes that used AO optics. One such , is the Neovar 2. I don't think they were marketed in North America but the optics and accessories would be compatible with a series 20, if in the case of the accesories they physically fit. The objectives are the same but spring loaded. The only other option is to change the head to a series 400 head. Then, any Reichert branded D.I.N. optics would work( lowering the stage makes the substage area pretty tight), as well as early Leica Delta optics and some HCX with adapters. Accessories could work too but may need adapters. Olympus oo objectives would also work with a 10% change in magnification and some Chinese D.I.N. oo, with the same proviso.

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Re: Wanted AO 20 compatible pieces

#3 Post by mnmyco » Tue Sep 17, 2019 6:01 pm

That is some great information, thanks. We had a discussion about the 1240 condenser with 1242 top lens a while ago. You determined that as a BF it was working around 1.3 NA aspheric and somewhere slightly less than 0.9 NA dry.


I assume though that those specs you found from testing include the screw in bottom lens on the 1240, which I am sadly missing. I am interested in doing some mix and match to max my NA on the condenser, as well as a Bertrand lens. What I was talking about with the ape rapture view though was the built in phase ring viewer that the phasestar had and I believe works on the series 20H as well. Oh, for the record, on the underside of the filter tray cover, the scope has 20 A stamped into it.

I wouldn’t mind trying my hand at fixing the trinocular if I found mirrors that work, but I think I need to buy one because I cannot rely on my ability to fix it to the level I want.

If anyone happens to have the cord and lamp I should probably buy that as well since I am getting worried about my inability to find it in my house.

I have been looking at that 50x DF with iris. I guess I would prefer dry, but I’ll take what I can get. As a mycologists I find 100x is typically too much for what I want, but 40x is disappointing. When I was doing my PhD we had a Leica with a great phase contrast 63x oil immersion with internal iris. Or we did until a certain lab member ruined it. Somehow he managed to damage the brass housing holding the lens in place.

Shoot me a PM if you are interested in selling. Just a heads up though, I may need to wait until after I get paid again Oct 5th. I am only paid once a month.



EDIT: There is a typo above. Should be “aperture viewer” not “ape rapture view” but “ape rapture” is funny enough I left it.

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Re: Wanted AO 20 compatible pieces

#4 Post by apochronaut » Wed Sep 18, 2019 11:20 am

Regarding the 1242 condenser. The observations I made were based on the condenser alone. I would think that the condenser works at around .95 dry abd when oiled , somewhere around 1.3. It cannot be used oiled for phase though because of the required focal point . Phase does not require an N.A. over 1. For BF, oiling is possible but probably overkill, since the functional N.A. of your 1.25 objective with a .95 condenser would be around 1.12-1.13 or so giving a difference in resolution at 500 nm of only be about .035 microns.

The lens in the bottom seems to be a negative lens to compensate for the differences in the distance of the field lens from the condenser, between the series 10 and the series 20. Due to this, the series 20 has a more classic kohler illumination system and the 10 has a modified Kohler illumination system, requiring the negative lens to set the field iris back some, in order for the condenser to properly focus it at the subject plane. The series 20, does not need it.

A couple of condensers you might consider keeping an eye out for are, the oil achromat aplanat models that they made over the years. The earlier one cat.#2110 is 1.30, used primarily in the DIC system and some fluorescence. The later one was the cat.#1973 , also used primarily for the same purposes in the series 400 microscopes. Both of these thread into the 1240 housing but the more modern one from the series 400 needs just a bit of a shim, in order to lift it's bottom edge above the iris. Physically, you can hardly tell them apart. The 2110 has a more polished exterior, the 1973 is brushed.

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Re: Wanted AO 20 compatible pieces

#5 Post by mnmyco » Wed Sep 18, 2019 1:10 pm

I’ve always read that the NA is always limited to the lowest part of the system. I did not think that there would be a “functional NA” in the manner you describe. Good info to know. And thanks for the condenser information. I will keep an eye out for those pieces. You are talking about just the lens part right? I think of the condenser as being the unit together, eg 1240 and 1242.


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Re: Wanted AO 20 compatible pieces

#6 Post by apochronaut » Wed Sep 18, 2019 7:29 pm

The resolution of the system is determined by the Rayleigh Criterion. R = 1.22 x λ/ N.A.objective+N.A.condenser, so the objective can rise above the limitation of the condenser due to the 1.22 constant in the formula.
There are other constraints, though. Slide thickness, coverslip thickness and more importantly sample thickness and it's refractive index all nibble away at the theoretical N.A. of an objective designed to overstep 1.0, with immersion. The higher the N.A. of the objective, the more perfect the variables in the illumination and preparation have to be in order for the objective to achieve it's theoretical limit. This is why water immersion objectives, which have a theoretical limit of 1.33 N.A. but are usually more along the lines of 1.15-1.25, often achieve superior performance to oil immersion objectives, which have a theoretical limit of 1.52 but are more often 1.25-1.40. Including water in the sample and the thicker the film the worse, is so unhomogeneous with the oil immersion system that it limits the N.A. severely, whereas with a water immersion objective the homogeneity of a water sample is better.

Condenser is the lens pack and it's housing. Condenser body is usually inclusive of the iris diaphragm. Often , the term condenser is used to describe the entire unit, including the lens pack , body and iris diaphragm. In the case of AO condensers, they were all threaded types, designed to fit on one or several bodies and the iris diaphragm was included as part of the body.
1240: condenser body with iris and carousel . 1242: condenser assembly. Other condenser assemblies will fit into the 1240.

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