MicrobeHunter.com Microscopy Forum

Hi folks,

While cleaning this condenser earlier, I noticed a "0,32" NA labeled on the lip of the main glass unit.



Is the top 1,4 NA element (465268) an auxiliary lens that can be removed, revealing the 0,32 element? If so, how - do you just push it up? As you can see, if I unscrew the unit, both the 0,32 and 1,4 NA elements come off together.

The Zeiss optics catalogue shows auxiliary lenses but on the previous generation Z condensers.

The n.a. 1.4 top lens usually unscrews from the 0,32 lens. It probably is stuck from gummed up immersion oil. Heating the lenses to 60°C for a while might soften the bond so it can be unscrewed.

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Agree, most probably dried out immersion oil gumming the works. The NA of both lenses line up above each other in all the ones I have seen.

I find damp leather gives a good grip, as does winding elastic bands around the part to be turned.
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The top 1.4 NA lens is removable. On my quite similar though earlier condenser. the bottom lens (the 0.32NA) is locked in place with three tiny (microscopic...) set screws. The whole front lens sub-unit is supposed to be dry, without grease.

Bob, I would hesitate to heat those lenses... maybe, if the two lenses are unscrewed and removed together as a single piece, the tricks of holding them with a stretched leather strap (as often suggested for the disassembly of faulty objectives) could be applied

Hi Doron,
of cause it is not ideal to put optical parts under stress, thermal or mechanical. But I think these lenses can reach 60°C when used with a powerful halogen lamp in warmer environment, so 60°C should be barely acceptable. I don't actually know whether there a cemented lens groups in these condensers, at least I haven't heard of any delaminations, so probably unlikely.

Bob

A bit of warming up should not be an issue. And as stated, good "grip" with some tools as described is essential, without applying too much mechanical tension.
Maybe one more hint: Also you can apply a small dop of WD40 on top of the 0.32NA lens. Right there where you can see the red 0.32 printing. You may turn the piece to rest on the top front lense. Give the WD40 some hours to reach the internal thread and to soften the grease or sometime corrosion debries. It is true that WD40 can be harmfull since it can easily reach optical surfaces...an in beetween. But it is moderate risk here if it is done carefully, it has helped me several times to remove such stucked front lenses.
Take care where you rest the optical surfaces, only small gaps, so ensure not to scratch them.

Rubber strap wrenches are cheap and ubiquitous. They are ideal for this application.

Thanks everyone for helping me out, I was able to unscrew the 1,4 NA element. Fortunately I did not have to resort to heating up / WD40 - just used rubber bands though it took quite some effort. There were brown hardened gunk which may be dried immersion oil.

Great ! congratulations.

I dislike oiling betwen the condenser 1.4 NA front lens and the bottom of the slide, but sometimes it is essential, particularly for dark field. So I wipe the oil right after the session.
Spills of water and salt solutions should also be avoided and wiped if they occur.

As long as they are kept dry and clean, seizure of these parts will not happen.