looking for condenser/diaphragm

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vasilis
Posts: 5
Joined: Mon Mar 16, 2020 10:40 am

looking for condenser/diaphragm

#1 Post by vasilis » Mon Mar 16, 2020 12:24 pm

Hello, this is my first post in the forum.

I have a Ernst Leitz Wetzlar microscope with the number 566090 in it's label (beside its brand) and I am missing it's condenser/diaphragm set. There is a ring-base under the stage and above the illuminator, whose height is adjusted via a knob. The ring base has a circular hand-screw used for holding tight the condenser/diaphragm set that fits on top (?) of the base. I have attached related photo (whole_microscope_web1.jpg), as well, as a 2nd photo of the microscope from above, just to make sure which model it is (above_web.jpg).

Also, I have attached a photo (disk_web.jpg) of a metal disk with a hole in the center, that I am not sure where it should fit and what it's purpose is. (I noticed that it can fit under the illuminator box, but I cannot think of any reason for that spot).
Attachments
whole_microscope_web1.jpg
whole_microscope_web1.jpg (59.44 KiB) Viewed 2482 times
disk_web.jpg
disk_web.jpg (10.63 KiB) Viewed 2482 times
above_web.jpg
above_web.jpg (17.7 KiB) Viewed 2482 times

apochronaut
Posts: 3084
Joined: Fri May 15, 2015 12:15 am

Re: looking for condenser/diaphragm

#2 Post by apochronaut » Mon Mar 16, 2020 12:55 pm

Your condenser mount is most likely a 37mm sleeve type. You don't need to find an authentic Leitz condenser , just one that fits a 37mm sleeve mount. The condenser must have an N.A. equivalent to the highest N.A. on your objectives, which will likely be 1.25 or 1.3.
If you have a very low power objective with an N.A. below .12 or so, it will require a wider angle condenser in order for the field to be filled with light. Condensers have various ways of doing that; removal of the high N.A. top lens, addition of an aux. lens below the condenser or having the top lens flip out of the way are the three common methods..

Lomo condensers are often very inexpensive and I think are 37mm. You might look into one of those. One other thing to consider is that some condensers are shallower than others. Although most condenser carriers have lots of travel and sleeve types can be raised and lowered in the mount, make sure the prospected condenser will reach the bottom of the slide when mounted.


Does the illuminator not have a pin in the bottom, to mount it? The disc looks like one that fits in a microscope base in order to take a mirror or illuminator, with a vertical pin rather than horizontal.


Here is a Lomo 1.2 condenser fitted with an aux. lens, which will work for up to 1.25 N.A. objectives and down to around .10 at least. 37mm.
https://www.ebay.com/itm/Condenser-ligh ... Swx3NZX0t2

vasilis
Posts: 5
Joined: Mon Mar 16, 2020 10:40 am

Re: looking for condenser/diaphragm

#3 Post by vasilis » Thu Mar 19, 2020 8:46 am

Hello and thanks for your helping tips. I have a few more questions:

- My condenser sleeve is approximately 38 mm in diameter (as I measured it with a caliper), having a pin screw that constricts it for mounting the condenser, so I reckon that I have a 37mm condenser sleeve, right?

- At the highest position of the condenser carrier travel, the carrier is approximately 17mm distant from the bottom of the slide, ie, it can get very close to the slide. Do you think that I should still check the thickness (ie height) of the prospective condenser in order to make sure that it will reach the bottom of the slide when mounted, as you wrote?

- I have 4 objectives:
1. Leitz Wetzlar - A 356738 - Fl Oel 54/0.95 - 170/0.17
2. Leitz Wetzlar - 45/0.65 - 170/0.17
3. Bausch & Lomb Opt. Co. - 4mm 0.65 - 43X - A D 6343
4. Bausch & Lomb Opt. Co. - APOCHROMAT - 16mm 0.30 - 10X
So I guess my highest-magnification lens is at 54X with an aperture 0.95 for oil immersion, right?
Will a 1.25 NA condenser fit for a 100X objective lens, in case I buy such an objective as well?

- What would be the specifications of a 100X objective for this microscope?

- Regarding the metal disc, the base has a vertical pin indeed, whose thickness fits exactly with the central hole diameter of the disc, so the disc fits on the pin, but I cannot see any reason of adding this below the illuminator box, since the last one fits on the pin alone, just fine. Could it's function be similar to a spacer's?

BramHuntingNematodes
Posts: 129
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: looking for condenser/diaphragm

#4 Post by BramHuntingNematodes » Thu Mar 19, 2020 12:23 pm

Interesting mix of objectives there. The b&Ls have a tube length of 160 so you might not be getting the best image out of them with a 170 setup. Leitz made an adapter called the plezy if you want to hunt some down.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

BramHuntingNematodes
Posts: 129
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: looking for condenser/diaphragm

#5 Post by BramHuntingNematodes » Thu Mar 19, 2020 12:29 pm

Hmm, actually it looks like the image should be fine the plezy is used to adjust parfocal distance. That might be a convenience, but I guess you really want to get a condenser first.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

apochronaut
Posts: 3084
Joined: Fri May 15, 2015 12:15 am

Re: looking for condenser/diaphragm

#6 Post by apochronaut » Thu Mar 19, 2020 1:04 pm

The reason that the condenser needs to get as close to the slide as possible is that it is necessary for the condenser to work at the highest possible N.A. , with very high N.A. objectives. Your 54X Leitz objective will require the condenser to be quite close to the slide. If you do obtain an objective in future, with an N.A. over 1, you will need the condenser very close as well, maybe even oiled to the slide , if you want maximum resolution. I would make sure when buying any prospective condenser that it is tall enough to reach the slide.

Your condenser requirement is for a 37mm size condenser.

It shouldn't be too hard to find a 100X Leitz objective , with 170mm tube. Leitz , made two series of 170mm tube objectives 37mm and 45mm parfocal. Yours are 45mm parfocal, so that is what you will need. The Bausch & Lomb 43X objective is fairly redundant in your system and as well is around 36.5mm parfocal. It would probably be a good idea to use it's hole in the nosepiece to carry a Leitz objective that fills your system out more fully. Having objectives of differing parfocal lengths is difficult to manage.

vasilis
Posts: 5
Joined: Mon Mar 16, 2020 10:40 am

Re: looking for condenser/diaphragm

#7 Post by vasilis » Thu Mar 19, 2020 4:37 pm

I appreciate your help. :)

vasilis
Posts: 5
Joined: Mon Mar 16, 2020 10:40 am

Re: looking for condenser/diaphragm

#8 Post by vasilis » Wed May 13, 2020 11:29 am

I just got a Lomo condenser for my microscope described above, but I have a slight-I hope- problem. The condenser has 36,5 mm diameter, whereas the holder ring has 38 mm diameter, so even if I tighten the screw, the ring still cannot hold the condenser in place. So, there is a difference of 1-1,5 mm. What would be the best way to make the ring diameter smaller, using some additional internal ring for example that would diminish the diameter and still keep the condenser in center?

I appreciate any tips.

apochronaut
Posts: 3084
Joined: Fri May 15, 2015 12:15 am

Re: looking for condenser/diaphragm

#9 Post by apochronaut » Wed May 13, 2020 1:36 pm

A split collar should work.....so that it compresses when the screw is tightened. Probably a section of a tomato paste can would do.

better would be to drill and tap the condenser yoke for 2 more thumb screws. You would get some benefit to be able to center the condenser some, with that mechanism.
It doesn't look like the original yoke has any centering capability.

BramHuntingNematodes
Posts: 129
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: looking for condenser/diaphragm

#10 Post by BramHuntingNematodes » Wed May 13, 2020 1:38 pm

An unsophisticated kludge I used to employ with astronomy optics was to wrap the small tube in electrical tape until it fit more or less snugly.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

vasilis
Posts: 5
Joined: Mon Mar 16, 2020 10:40 am

Re: looking for condenser/diaphragm

#11 Post by vasilis » Wed May 13, 2020 6:48 pm

Thanks for the replies! For the moment I used some electrical tape and the condenser fitted tightly inside the ring base. It cannot reach it's lowest height of it's travel, because it bumps on the light fixture, but it can travel all the way up the underside of the slide. I don't suppose that there will be any problem from the fact that it cannot travel to it's lowest height (it can travel about 6-7 mm above it's lowest height), will it?

The condenser also has an additional lens underside which you can remove it or add it by rotating it and another rotating ring above the additional lens, which I suppose is for adding a filter?

Another question I have is, should I add a trimmer in the lighting fixture, so I can regulate the light intensity? I have read that it is wrong to do this with the condenser, since the diaphragm changes the field depth and contrast and is not right for regulating the light intensity.

BramHuntingNematodes
Posts: 129
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: looking for condenser/diaphragm

#12 Post by BramHuntingNematodes » Wed May 13, 2020 6:57 pm

Either a dimmer or ideally some neutral density filters or best of all both.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

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