AO-Reichert 1973A condenser DIY help request

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mnmyco
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AO-Reichert 1973A condenser DIY help request

#1 Post by mnmyco » Sat Oct 05, 2019 12:38 am

I have managed to find the housing and top lens for a 1973A 1.4 NA achromatic condenser. I know that Apo has made a DIY version with these pieces in the past. So, I am soliciting help and advice for attempting some sort of rebuild.

I’m a bit l lazy, but if anyone is interested I will find the eBay listing again. The seller should have 3 left. They also have four top lens elements that I believe to belong to the 1973A condenser, but lack the condenser body for those.

For the three remaining housing+top lens, here is the eBay item number: 264270037838

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Re: AO-Reichert 1973A condenser DIY help request

#2 Post by apochronaut » Sun Oct 06, 2019 5:12 pm

Subsequently, I did find complete #1973 condenser units. The diy ones that I built up, using the 1973A condenser lens housing and 1.4 N.A. top lens, ended up being improved dry condensers. Their performance as oil condensers, did not exceed the performance of a # 1973 condenser when oiled but they do exceed that of the # 1201 .90 achromat aplanat, which makes them very practical everyday condensers with all but the very best high N.A oil . planapo objectives.

One of them also holds promise as a water immersion type but I haven't fully tested it against it's dry self yet.

What made that project a highly acceptible one was that the seller was willing to sell those # 1973A blanks for peanuts but also sold me the bare lenses I wanted to use to complete the designs for peanuts too. Each condenser didn't cost any more than about 40.00 to make.

mnmyco
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Re: AO-Reichert 1973A condenser DIY help request

#3 Post by mnmyco » Sun Oct 06, 2019 11:36 pm

I have purchased a 1201 as well, but the seller did email me and let me know he included what is believed to be the other lens for the 1973A. Once I get it I will post here and let you know what materials I received and what you think I can do with those. I am unclear if all the pieces, besides the lenses, were sent.

MNMyco

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Re: AO-Reichert 1973A condenser DIY help request

#4 Post by apochronaut » Mon Oct 07, 2019 1:07 pm

You are lucky to be offered at least one of the other lenses but finding an accurate further lens would be very difficult.
The 1973 condenser contains 5 lens elements in 3 groups. In addition to the top cell assembly, which is a type of achromatic doublet, there is a middle cell meniscus lens and a bottom cell achromatic doublet . These are precision fitted in mounts and held in registration by a threaded retaining ring.

I do not know for sure but suspect that the difference between the 1973 and the 1973A is that the A has been tested and designated as strain free otherwise the actual lens systems are the same.It would have been the condenser used for some POL , and all DIC applications.

mnmyco
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Re: AO-Reichert 1973A condenser DIY help request

#5 Post by mnmyco » Tue Oct 08, 2019 3:11 am

I am a bit unclear on what was sent, but from the sellers email is sounds like he sent everything. Apparently, they have 20+ pieces, but are not all complete and in unknown condition. So, they don’t advertise them as complete. The image shows the housing and the top lens set in the brass piece.

We will see what happens. Should be here tomorrow.

MNMyco

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Re: AO-Reichert 1973A condenser DIY help request

#6 Post by apochronaut » Tue Oct 08, 2019 1:19 pm

I don't see an image. Is this silosurplus or sepresin ?

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Re: AO-Reichert 1973A condenser DIY help request

#7 Post by mnmyco » Tue Oct 08, 2019 5:35 pm

Silosurplus

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Re: AO-Reichert 1973A condenser DIY help request

#8 Post by mnmyco » Fri Oct 11, 2019 4:58 am

Finally arrived today. Seller included the bottom cell of elements, but it is still missing the middle cell. If the 1973A shares the same number and layout as the 1973. Apo, if possible, could you post a photo of the separate parts of the condenser? I would like to show the seller In case he does have the middle element and retaining ring. If you have any other suggestions I would like to hear them.

I hate to merge thread topics, but I am curious; do you know the condenser in this eBay listing?

https://www.ebay.com/itm/Spencer-Americ ... SwwZJcc1OW

I bought the same thing for $50 from a different seller. Just curious as it has no catalog numbers on it.

Thanks,

MNMyco

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Re: AO-Reichert 1973A condenser DIY help request

#9 Post by apochronaut » Fri Oct 11, 2019 1:50 pm

That would work on the series 15/35 through the 2/4, for sure. Basically, all of the post war lab scopes with a 160mm tube. The red lettering designates it as having been tested for strain. Has the polarizer. The microscope it is probably from is the series 2/4 Polstar. S.F. objectives are scarce for those, as are the eyepieces with red lettering but they may have used only the # 177 huygens type , so strain isn't a factor because they are only 2 element.

Could you post a picture of the bottom doublet they sent for that condenser? The retaining ring will be almost impossible to find. One thing is that AO used almost entirely U.T. S. threads. Most such retaining rings one might come across would be metric.
When I retrofitted those two barrels into the two high N.A. dry condensers that I made, I used rubber O-rings as seats for and to seal in the bottom lenses and it works well. I am pretty busy right now but mid week of next, I will try to post pictures of them broken down, as well , I will try to get the dimensions of the meniscus lens in the 1973. One thing you don't know , is the type of glass it was made from, something quite critical in maintaining it's achromatic specification.


A little taste of what they were doing with glass.
https://patents.google.com/patent/US2716069A/en

Here is the patent for the precursor, 2110 condenser, a 1.30 version but otherwise almost identical.
http://www.freepatentsonline.com/4060306.html I suspect that securing a patent based on the small differences between the 2110 and the 1973 would have been unlikely.

mnmyco
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Re: AO-Reichert 1973A condenser DIY help request

#10 Post by mnmyco » Fri Oct 11, 2019 6:07 pm

Here is what I was sent. Very tight fit. If they are the right parts they are not from the same housing as the one that was sent.
Thanks for the info on the polarizing condenser. I figured that is was red meant. Interestingly, that condenser has the notch to fit on the fork of my series 10 and 20. I checked and it does fit on that fork in the proper place. The one I bought does not have the swing out lens nor does it seem to have a spot to attach one. Either that, or the threads in the hole have been stripped to the point it no longer looks threaded. It does have a nice slide in filter holder on the bottom, and although there are no markings, you can rotate the polarizing filter 360 degrees.

Image

Thanks

MNMyco

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Re: AO-Reichert 1973A condenser DIY help request

#11 Post by apochronaut » Mon Oct 14, 2019 4:33 pm

The picture is very fuzzy but they look correct. The fit is supposed to be very snug in the bore. You just have to get each cell into correct alignment in the barrel and very gently push them up to their required location. The pressure needs to be very light but with correct alignment. If the cells do not move with light pressure then they are slightly cocked in the barrel. If you push to hard when so, the cells will lock into a cockeyed position and need to be forced a little from above, in order to get them back out.

Yes. That polarizing condenser has the same dovetail as the series 10 or 20. They used the same dovetail from the series 15/35 through to the 10/20, so it will fit the 10/20. That particular condenser was for the 2/4 though. I am unsure if it is focusable to a Koehler condition on the series 10 or 20. The 20 is more of a classic Koehler illumination system, whereas the 10 is a modified Koehler, with a very short distance between the field iris and the condenser.

mnmyco
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Re: AO-Reichert 1973A condenser DIY help request

#12 Post by mnmyco » Mon Oct 14, 2019 6:01 pm

Not sure why the image is fuzzy. It wasn’t when I posted it. I am missing a lens element though, aren’t I?
Last edited by mnmyco on Tue Oct 15, 2019 6:15 pm, edited 1 time in total.

apochronaut
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Re: AO-Reichert 1973A condenser DIY help request

#13 Post by apochronaut » Mon Oct 14, 2019 8:44 pm

yes. there is a meniscus lens. Give me a few days and I will take the 1.3 N.A. condenser and the 1.4 apart and see what the differences are . Some extrapolations about the meniscus lens for the 1.4 might be possible by comparing the meniscus lens of the 1.3 N.A. condenser to the specifications in the patent I posted the link to.

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