Wanted: Stray light cap for Leitz dry darkfield condenser

[ProtistAdmirer]

Hi all,

I now have a Leitz dry darkfield condenser for my Dialux, but am still in need of the black plastic(?) stray light cap or hat that goes with it. Does anyone have one they’d like to sell me? I will pay $40 USD for it. Thank you!

[Sabatini]

Hi, I have a similar one. But that plastic piece is kind of stuck, and I know it's okay to remove it.
What happens to the condenser without that plastic part? ? Or rather, what can you do with the condenser without that part? Is the condenser useful in any way without that plastic part?
Or is the plastic part completely necessary to achieve the dark field?
Thank you for your attention.

[ProtistAdmirer]

You can use the darkfield condenser without the light cap, and it works well at lower magnifications. But for the 40x objective, it is recommended to use the cap to block stray light. I’m getting glare and difficulty getting full darkfield without it when I use the 40x objective. One source I saw even said to use it all the time. I don’t know, as I don’t have one to experiment with.

[MichaelG.]

Here’s a brief but helpful note from the DIALUX Instruction manual:
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MichaelG.

[ProtistAdmirer]

Yes, that’s one of the sources I read, thanks for digging that up! It does seem like the cap will help with the 40x.

[ProtistAdmirer]

They also talk somewhere about funnel stops that fit within the objective, which I’ve never seen offered up for sale, and then the IRTIS iris attachment which affixes to the objective somehow. I actually have the IRTIS, but I think it needs a special objective. I can’t see any way to attach it to my regular Leitz 40x objective unless it comes apart somehow.

[ProtistAdmirer]

Photo of IRTIS iris (and funnel stop) from one of the Leitz manuals. It looks like the objective comes apart or is a special objective that goes with the IRTIS. Anyone know?

[MichaelG.]

It looks like a simple concept ... but some of the Leitz detailing is verging on the obsessive.

Presumably you have this:
http://www.science-info.net/docs/leitz/ ... denser.pdf
... but those who land here in the future may find it useful.

MichaelG.

[Sabatini]

Thank you very much for your kind and precise information about the function of this plastic part.

[ProtistAdmirer]

... those who land here in the future may find it useful.

MichaelG.

Excellent. We are having quite a discussion for the “Wanted to buy and sell” area, but someone will stumble across this stuff in a future search.

[patta]

Can you sketch a drawing or estimate the size of this cap? At least the outer diameter d1. So i can design it and you can order it 3D printed from some shop nearby you.

Meanwhile, you can just try to cut a disc of cardboard, it may be enough already.

For the next generations, it will be very useful to have the CAD drawings of all those small vintage components

[MichaelG.]

Can you sketch a drawing or estimate the size of this cap? At least the outer diameter d1. So i can design it and you can order it 3D printed from some shop nearby you.

Meanwhile, you can just try to cut a disc of cardboard, it may be enough already.

For the next generations, it will be very useful to have the CAD drawings of all those small vintage components

Great idea

Unfortunately mine is ‘in storage’ at present
... when I eventually retrieve it, I will post some dimensions [if still required]
... please don’t hold your breath though !

MichaelG.

[ProtistAdmirer]

Can you sketch a drawing or estimate the size of this cap? At least the outer diameter d1. So i can design it and you can order it 3D printed from some shop nearby you.

Excellent, thank you Patta! This would be great. I’ve tried darkfield stops, coins, etc. sitting on top of the condenser but with imperfect results so far.

[ProtistAdmirer]

... when I eventually retrieve it, I will post some dimensions [if still required]
... please don’t hold your breath though !

MichaelG.

I’m sure I’ll still be waiting whenever you get to it! Ha. Thank you!

[patta]

Thanks for the enthusiasm!
I've tried to reverse-engineer the stray light cap from the illustration in the Leitz manual.
If the illustration is true, you can generate the cap only from the measure of the iris diameter. If the illustration is not realistic, well, you have to take all the weird geometry measurements.

I've put the two drawings on Thingiverse, from which you may generate the plug with "Customizer" and download the .stl for 3D printing. Beware that Thingiverse sometimes work, sometimes is offline..
Fixed design (as from Leitz catalogue illustration):
https://www.thingiverse.com/thing:4572140
Open design (put your measurements):
https://www.thingiverse.com/thing:4572365


The code is also in the more reliable GitHub, but then you need to install OpenScad yourself:
https://github.com/pattarini/CAD/tree/L ... enser_plug

[ProtistAdmirer]

Wow, thank you for doing that! Super cool! For dimensioning, there is no iris on the darkfield condenser, but the diameter of the bottom opening that admits light is 18 mm. See attached photo. I am not sure if this corresponds to the Leitz drawing or not... there is a little bit of uncertainty there. If anyone else has this cap and wants to measure it, please do! Thank you, Patta, for your work. It may be possible to verify dimensions using photographs as well. I will look into that.

[MichaelG.]

I have just returned from an expedition into the wilderness of my ‘storage’

My lovely Leitz D 0.80 condenser has no plastic insert with it

Apologies for raising false expectations ...

MichaelG.

[ProtistAdmirer]

My lovely Leitz D 0.80 condenser has no plastic insert with it
MichaelG.

Well, it sounds like you’re definitely not alone in that! Thank you for checking, that was nice of you.

[patta]

My lovely Leitz D 0.80 condenser has no plastic insert with it

Oh no!! did this plastic thing ever existed? Is it made of Unobtanium?

I attach here a pdf (the second) with some possible plug profiles, based on the iris measurement and Leitz catalog image18mm plus minus.
You may print it (on paper) at real size, cut the profiles/disk and check which fit best. Just realized that the pdf is large, but you can print only an A4 /USletter crop with the profiles.

Giorgio

[ProtistAdmirer]

Maybe it’s a myth!

Thanks again for making these drawings, Giorgio! Definitely above and beyond!

[Sabatini]

Unfortunately I have not been able to remove mine from its place. As I indicated they are attached. Probably the paint was removed with some solvent, ethanol or xylol...but if I can separate it I would send you the information of the measurements.
Good luck.

[MichaelG.]

Permit me, please, to get all Biblical :

Rejoice with me, for I have found ... the little black cap that was lost !

I will measure and photograph it tomorrow.

MichaelG.

[ProtistAdmirer]

Praise the heavens, which hath delivered unto us this manna!

[patta]

... and He separated the light from the dark.

[MichaelG.]

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Let’s not mention Erich von Däniken ... but the profile looks remarkably like the classic flying saucer:
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profile

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and here is the interior view:
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interior

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Dimensions [to the best of my ability today]:

Outside Diameter = 25.28 mm
Thickness at Rim = 0.40 mm
Bowl Diameter [Outside] = 18.60 mm
Bowl Diameter [Inside] = 18.14 mm
Total Depth = 10.21 mm

I am still unsure whether this is a very high quality plastic moulding, or a pressing from non-ferrous metal.
... Sorry but I am not prepared to section it, to find out

MichaelG.

[Hobbyst46]

I am still unsure whether this is a very high quality plastic moulding, or a pressing from non-ferrous metal....

If it is a flying saucer, it is probably metal.
Otherwise, if it can be weighed, with at least some accuracy, the heaviest plastics (of that time) had less than half the density of a metal (say, aluminum). That is, densities of <1.4 vs 2.7 g/cc, respectively.

[MichaelG.]

First rough weighing shows 2g
... my chemical balance is out of commission at present, so I’m sorry, that’s the best I can do.

It does feel cool when briefly touched to the lips, and the dull black finish is excellent, so I am leaning towards brass or bronze.

Happy to be proved wrong though !

MichaelG.

[Hobbyst46]

Sorry, whoops,
erroneous calculation !!!

[Hobbyst46]

Revised calculation
The net volume of this colonial tropical cork hat is estimated as 0.176 ccm.
(based on the above dimensions and taking the rim to be a flat ring; and assuming that the thickness of the bowl is derived from the outer and inner diameters, that is, {18.60-18.14}/2 = 0.23). If the weight is 2 g the density would be ~11. So, probably brass (which is 8-9).

[ProtistAdmirer]

OMG, I love you guys! This is so great!