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 Post subject: $30 mystery condenser
PostPosted: Thu Dec 06, 2018 12:23 am 
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Hi folks,
Can anyone tell me what kind of condenser I bought for $30 on eBay? It works nicely with my 4x objective for dark field (enough reason to keep it) - but not much else despite the NA 1.25 and 10x marking on the condenser? For it to do dark field at higher mags do I need to use oil between it and the bottom of the slide, maybe I need a special (oil) eyepiece too.
Please kindly advise and thanks for reading this.
Jimmy


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PostPosted: Thu Dec 06, 2018 12:38 am 
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You would have to post some more pictures, principally from the top and the bottom, in order to deduce just what it is, unless someone happens to have had experience with one like it.

The specification 1.25 immediately implies that it is an oil immersion condenser but that kind of flies in the face of it being also designated for 10X.


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PostPosted: Thu Dec 06, 2018 1:29 am 
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It's part of a phase condenser system, like this one:

https://www.ebay.com/itm/Phase-Contrast ... rk:14:pf:0

The darkfield effect is apparently just from the stop effect of the condenser phase disk.


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PostPosted: Thu Dec 06, 2018 3:09 am 
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Sorry, I took a couple photos but all were way too large. Here's a photo of the bottom and top, reduced in size to enable UL.
Thanks again


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kelley condenser top.jpg
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kelley condenser bottom.jpg
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PostPosted: Thu Dec 06, 2018 3:23 am 
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wporter wrote:
It's part of a phase condenser system, like this one:

https://www.ebay.com/itm/Phase-Contrast ... rk:14:pf:0

The darkfield effect is apparently just from the stop effect of the condenser phase disk.


Sure looks like it but it doesn't show bottom. It mentions annalus ring


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PostPosted: Thu Dec 06, 2018 7:13 am 
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apochronaut wrote:
You would have to post some more pictures, principally from the top and the bottom, in order to deduce just what it is, unless someone happens to have had experience with one like it.

The specification 1.25 immediately implies that it is an oil immersion condenser but that kind of flies in the face of it being also designated for 10X.


I'm just a newbie but that sounds correct to me Apochronaut. I may just try a drop of oil under the slide and see what I can see. Hahahaha, for $30 I knew I was buying a pig in a poke, an unknown "gizmo".


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PostPosted: Thu Dec 06, 2018 7:24 am 
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wporter wrote:
It's part of a phase condenser system, like this one:

https://www.ebay.com/itm/Phase-Contrast ... rk:14:pf:0

The darkfield effect is apparently just from the stop effect of the condenser phase disk.
Well spotted!

I am afraid oil is not going to make much difference as what you have there is the 10x phase objective attachment.
I recommend that you contact the seller and per wporter's link you inquire as to the rest of the kit.

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Last edited by 75RR on Thu Dec 06, 2018 9:46 am, edited 1 time in total.

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PostPosted: Thu Dec 06, 2018 7:45 am 
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Wild irrational guesses:
This is probably a PC condenser that teams with the 10X PC objective ("Ph 1") to produce PC. As such it would be used dry.
But, alternatively, from the photo, the phase annulus seems to be relatively large, say 6mm diameter and should rather actually team with the 60X-100X PC objective ("Ph 3"). It would then provide darkfield with the 10X objective, especially if oiled.

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PostPosted: Thu Dec 06, 2018 8:43 am 
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This might be a mix of components: N.a. 1,25 wouldn't be used for a 10:1 objective and if Doron is right, the phase stop might actually fit to a stronger objective. So perhaps condenser, stop holder and stop were not originally together in this combination.
So what can you do with it? If you have phase objectives and a phase telescope you might check whether the condenser fits to one of them. For birght file use you would need an adjustable condenser aperture. With the right stops you can use it for dark field for objectives up to 20:1, with luck 40:1.

Bob


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PostPosted: Thu Dec 06, 2018 10:50 am 
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Hmm, looks like a mismatched marriage of parts to me.....

John B.

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PostPosted: Thu Dec 06, 2018 10:55 am 
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wporter wrote:
It's part of a phase condenser system, like this one:

https://www.ebay.com/itm/Phase-Contrast ... rk:14:pf:0

The darkfield effect is apparently just from the stop effect of the condenser phase disk.


Everyone! ... This has been identified and solved by wporter See above link:

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PostPosted: Thu Dec 06, 2018 10:59 am 
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Haha! That's the exact one - goodness I love this forum!

Jolly well-met wporter old chap!

John B. :D

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PostPosted: Thu Dec 06, 2018 12:16 pm 
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Thanks wporter for the identification.
Why would a 21th (or late 20th) century microscope maker design three separate PC units for the objectives, and not a combo aperture-darkfield-phase/DIC turret condenser, like major manufacturers did 30 years before ? Now, to change phase 10X to 40X one needs to pull out the condenser, replace a part in it, re-insert it, then re-align/re-center ? am I missing something ? or is it just as commented by Apochronaut in another thread, about Stencil microscopes ?

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PostPosted: Thu Dec 06, 2018 1:24 pm 
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A phase condenser like your Zeiss one would still cost a lot to make even with chinese production costs. There is also more that can go wrong when the condenser is not made to the highest specification. These pop-in phase stops should work acceptably well and cost probably 1/4 to 1/3 to make.

Does somebody have a quality phase condenser from the 50s to 80s and can compare it to one from the last decade? I could imagine that the newer one is simpler made even with the top brands.


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PostPosted: Thu Dec 06, 2018 2:12 pm 
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There were numerous brands that had as their cheaper phase option a standard abbe 1.25 condenser that could have separate phase annuli fitted into it, one by one. This was often for use with a system where only one phase magnification was necessary( often 40X for blood counts or the like) and you see on the used market, stands fitted with 10x, 20x, 40x, 40x ph, and 100x objectives. Usually the annulus went in as a slider and then could be locked into the out position so the condenser could be used as an abbe, oiled or not. This is a cheaper version of that but it looks like the phase annuli is threaded onto the bottom, one by one. That was the oddity of the design that threw me. It looks so cumbersome to use but now I remember having seen similar included in entry level systems. I have also come across abbe condensers that have a thread on the bottom but no iris diaphragm before.
The other thing that threw me was : why a 1.25 N.A. condenser? That is by it's nature an oil condenser but phase is effected unoiled or at least an N.A. over 1.0 is unnecessary. The only answer I can think of is that the condenser existed as a production unit already, with a threaded on iris diaphragm unit and was brought into use also as a thread on phase system.

For those interested in diy'ing a whole range of other contrast systems ; all kinds of masks, one of those with a group of the annuli housings might be ideal, because each one comes with a set of centering screws, especially ideal for those making the difficult to center DF stops.


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PostPosted: Thu Dec 06, 2018 3:58 pm 
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Quote:
For those interested in diy'ing a whole range of other contrast systems ; all kinds of masks, one of those with a group of the annuli housings might be ideal, because each one comes with a set of centering screws, especially ideal for those making the difficult to center DF stops.


That's a good idea, Apo; much easier than working on modifying a turret phase condenser, and it would also lend itself to making a variable slit-plate for modulation contrast experiments.


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PostPosted: Fri Dec 07, 2018 3:58 am 
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Thank you all - very grateful that you pros took the time to reply.
Just for the record, this ugly step-sister condenser does a pretty good dark field using 4x objective. (I'll take some pics and post them) It only cost $30 and the eBay seller made no claims so I will keep it. I would only add, I swapped the top lens with the stock condenser lens included with my Omax Trinocular microscope. No luck at any mag or any condenser height... It is all metal, very heavy and could serve as an outstanding paper weight too. ;-)

I agree, it is cannibalized from some other sets apparently. Live and learn. Once again thank you all for the great info.
Take good care,
Jimmy


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