TheSkySearchers

I'm interested in buying a few Carl Zeiss Jena microscope eyepieces to use with my 60mm telescopes using .965" accessories. I don't understand how to find the focal length if it is not indicated on the eyepiece.

For example, how do I find out the focal length if the eyepiece only has the following information: Kpl 10x, Kpl 16x. Or K 5x. Or MF Projektiv 4.1 or 6,3. I have found others that are designated as C-10x, PK-10x, K-18, Homal II f = -70, etc.

I found one that was K 7x and focusable, 23,2mm. Does that mean it is 23.2mm focal length?
Thanks!
Bruce

The standard is that Zeiss uses a fixed 250mm objective focal length. So a 25mm fl eyepiece gives a magnification of 10x. So a 7x eyepiece should have a focal length of 35.7 mm. So I am puzzled by your report of 23.2 and suggest you perhaps measured something other than the true focal length.

Here is a link to the Zeiss nomenclature:

https://www.zeiss.com/microscopy/us/sol ... lanes.html

As you can see things are done differently in microscopy. In any case a K-7x would have a 35.7 mm focal length.

250 is the most commonly used number for working out microscope eyepieces.

Lady Fraktor wrote: ↑Wed Apr 07, 2021 10:07 pm 250 is the most commonly used number for working out microscope eyepieces.

Yes. Divide 250mm by the eyepiece magnification to get the eyepiece focal length. For the K-7x that gives the result I note above.

notFritzArgelander wrote: ↑Wed Apr 07, 2021 9:52 pm The standard is that Zeiss uses a fixed 250mm objective focal length. So a 25mm fl eyepiece gives a magnification of 10x. So a 7x eyepiece should have a focal length of 35.7 mm. So I am puzzled by your report of 23.2 and suggest you perhaps measured something other than the true focal length.

Here is a link to the Zeiss nomenclature:

https://www.zeiss.com/microscopy/us/sol ... lanes.html

As you can see things are done differently in microscopy. In any case a K-7x would have a 35.7 mm focal length.

Thank you, that explains it for me! Now I see that the 23,2mm is listed as the diameter! Sorry, I misread it.

What does the designation MF Projektiv, Kpl, K, C, PK, and Homal stand for?
Thanks!

Lady Fraktor wrote: ↑Wed Apr 07, 2021 10:07 pm 250 is the most commonly used number for working out microscope eyepieces.

That tells you how much microscope experience I have!!!! Good to know finally!

StarBru wrote: ↑Wed Apr 07, 2021 10:38 pm What does the designation MF Projektiv, Kpl, K, C, PK, and Homal stand for?
Thanks!

Sorry I am less help here. Maybe @j.gardavsky gardavsky who is much better versed in microscopy can help. I could guess that the K is for Kellner and the C is for a simple convex lens? But these are worthless guesses. Don't buy them unless someone with a better grasp of microscopy chimes in.

Denis gives a very good explanation of the different Zeiss types and it saves me a lot of typing as I do not have to repeat him
https://www.cloudynights.com/topic/5119 ... elescopes/

notFritzArgelander wrote: ↑Wed Apr 07, 2021 11:16 pm

StarBru wrote: ↑Wed Apr 07, 2021 10:38 pm What does the designation MF Projektiv, Kpl, K, C, PK, and Homal stand for?
Thanks!

Sorry I am less help here. Maybe @j.gardavsky gardavsky who is much better versed in microscopy can help. I could guess that the K is for Kellner and the C is for a simple convex lens? But these are worthless guesses. Don't buy them unless someone with a better grasp of microscopy chimes in.

Zeiss Jena (CZJ) and West eyepieces:
CZJ Homal is the negative focus projective lens assembly, a predeccesor of the barlows for imaging, and conceptually it is also a predecessor of the field booster in TV Delos
CZJ MF Projektiv is an imaging eyepiece
CZJ PK and K are Abbe orthos with the planar (P) and with the CVD correction (K). It is the only Zeiss Abbe ortho (field stop - 3 - 1) for the microscopes since the old Zeiss times, and it corrects the residual chromatic aberration of the fuoride microscope objectives. The PK have been manufactured as a complete set of focus lengths, and all of them Abbes.
Zeiss West Kpl, C are the Zeiss West versions of the correcting (CVD), and eventually planar eyepieces. Their different focus lengths used to have different optics designs.

Otherwise, I have put into the denis' thread on the CN more infos and technical specs, scroll through https://www.cloudynights.com/topic/5119 ... pes/page-9
In my collection, I have some of these Zeiss West eyepieces manufactured in Göttingen still boxed and unused, obtained from the surplus reserves in Germany,
https://www.cloudynights.com/gallery/im ... -pl-10x23/
https://www.cloudynights.com/gallery/im ... -44-40-34/
https://www.cloudynights.com/gallery/im ... 16-455048/

Together with others, they document the product and devolpment history of the Göttinger designs throughout two generations of the glass materials - before 1990, and since 1990.

Best,
JG

Thank you, JG, Lady Fraktor, and notFritzArgelander, for all this information! I cannot afford the most expensive microscope eyepieces, but maybe I'll get lucky finding the less expensive CZJ K versions.

WOW! And I thought telescope EPs were complicated. Thanks all of you for the lesson. Good luck in your search.

StarBru wrote: ↑Thu Apr 08, 2021 11:35 pm ... I cannot afford the most expensive microscope eyepieces, but maybe I'll get lucky finding the less expensive CZJ K versions.

Hello Bruce,

the Zeiss West E-Pl and W-Pl can be found preowned on the eBay in Germany for less than what you pay for a new TV Plössl,
https://picclick.de/Okular-zeiss-e-pl-1 ... 31654.html

and similarly the Leica HC Plan,
https://www.ebay.de/itm/174200849433?&m ... 0dc3732fd3
With the Leica eyepieces it is important to check out where they have been manufactured, as some of the manufacturing has moved to the Leica plant in Singapore, and they have other glass materials inside.

Best,
JG