Hello,

I've got a Xenar 180/4.5 (marked Schneider-Göttingen Xenar 1:4,5 F=18cm) in a barrel with no aperture. It was pretty dirty, but I was able to disasemble and clean both groups nicely. I can work around the lack of shutter, but I'd like to modify the barrel to accept waterhouse stops. I'll have a machinist cut the slot, but I am stuck determining the proper position. Can anyone point to a lens schematic or another source to give me the spacing between the aperture and front/back groups?

Thanks in advance!