help understanding objective specs

[rs6000]

Hello I picked up this older zeiss 40x objective at dayton,Oh Hamfest several yrs ago and only recently decided to put together a scope to use it in
but that brought up more questions.

I have found 2 items I cant get my head around no matter how I search the web

1. in the attached pictures there is lettering M.J have no idea what it translates too all docs I have searched have no reference to this one.


2. if this is a 40x objective why does the zeiss catalog state it has initial magnification of 100x all other objectives on list the X ratio corresponds properly to the initial mag column??
I guess I don't understand this initial magnification thing very well LOL.

cheers

[Hobbyst46]

The objective in the photo is a 40X magnification. Oil immersion. NA 0.6-1.0. This adjustable iris feature enables nice darkfield. I guess the m.J (on my objective it is marked as m.I) means with iris in german but that is a wild guess.
Anyway, the catalogue page refers to a 40x/0.95, used dry, not immersion, with correction collar to accomodate a range of coverslip thicknesses 0.11-0.23 mm. This is NOT the objective in the photo.

The entry below that describes an objective somewhat similar to the one in the photo but there are typo errors in the entries of the 40X/1.0 description and the 100x/1.3 with iris, three lines below the 40x. ( who am I to point to discrepancies in this time honored catalogue). An 40X objective has an initial mag of about 40 and the same goes for other mags.
Besides, the catalogue refers to an objective designed for a 0.17mm thick coverslip. Yours can be used with any thickness of coverslip.

[rs6000]

Its the Same Objective apo 40x oel with 2 lateral side views

I was just trying to capture different angle to show all pertaintent Data markings on barrel

[Hobbyst46]

I have slightly edited my previous reply. Your objective, the one in the photo, is indeed a 40X/1.0 NA objective with iris so it is actually 0.6-1.0 NA . The coverslip thickness does not matter. It is not mentionex in the catalogue page you posted.

[rs6000]

Oh so this is not a plan objective
I thought for the money they were asking for this back in the day plan correction would be expected?

have any idea what year this was out my catalog was date 1974

[Hobbyst46]

Oh so this is not a plan objective
I thought for the money they were asking for this back in the day plan correction would be expected?
have any idea what year this was out my catalog was date 1974

From the photo it indeed looks like the objective is not Planapo but Apo. The only (old, finite 160mm optics) "Zeiss West"/"Carl Zeiss" (NOT Zeiss Jena) objectives I know have been Planapos.
Can you post photos from other angles around the objective, that show the catalogue number, manufacturer name etc? it might make it easier to locate it in catalogues. There is a web compilation of many old Zeiss catalogues.

[rs6000]

Thank you I never thought of looking at the number on the barrel

[Hobbyst46]

Sorry rs6000,
I searched old Zeiss catalogues that I had downloaded but failed to locate this objective. It is unusual in (1) that it is Apo rather than Planapo and (2) bears a strange five figure identifier - not the six-figure catalogue number as for more ubiquitous Zeiss objectives. Hope that the Zeiss experts will respond.

[ImperatorRex]

Hi,
FYI: found a reference for an "Apochromate 40/1,0 Oil mit Iris" in an Zeiss Standard GFL manual.

[Hobbyst46]

Thanks Jochen! Indeed, the catalogue entry you mention is for a 40X/1.0 Apo 160/-.
I feel stupid - my own scope is a GFL, and I have the original manual...
In my defense, the objective in the posted photo does not bear the "correct" catalogue number of 461736... poor defense it is...

[apochronaut]

I didn't notice this thread earlier and although it seems that it is solved, I thought I would mention this..
I have had on 2 occasions , Leitz objectives that were stamped Meth. Jod. for methylene iodide immersion. Methylene iodide is a rather viscous oily liquid with a super high refractive index. I wonder whether Zeiss referred to this an an oel objective but qualified to use methylene iodide as the oil?....hence the differing cat. #.

[Hobbyst46]

I didn't notice this thread earlier and although it seems that it is solved, I thought I would mention this..
I have had on 2 occasions , Leitz objectives that were stamped Meth. Jod. for methylene iodide immersion. Methylene iodide is a rather viscous oily liquid with a super high refractive index. I wonder whether Zeiss referred to this an an oel objective but qualified to use methylene iodide as the oil?....hence the differing cat. #.

Sounds good! That might explain the "/-". For use with methylene iodide directly between the specimen and objective, without cover slip. Only that the engraving on the posted objective is m.J (I think, it should have been M.J as for the Leitz).

[75RR]

Hi,
FYI: found a reference for an "Apochromate 40/1,0 Oil mit Iris" in an Zeiss Standard GFL manual.

In German, the capital letter i is often written as 'J'. This would make m.J an abreviation for mit iris (with iris). As in incorporating an iris to permit N.A. reduction for darkfield.
Similarly those of us who have Zeiss Phase condensers tend to refer to the brightfield port as the 'J' (jay) port. It is in fact the 'i' for iris port.