Optically the eyepieces seemed o.k., but something about the diopter mechanics just didn't seem quite right. Both eyepieces rattled, if I gently shook them from side to side, but went silent if I also pushed or pulled the inner lens capsules.
The worse rattler had 0.1mm (0.004") play, side to side, at certain diopter settings.
Here are pictures of the fully-extended eyepieces, after I removed their lower plastic tubes that hold a reticule:
This is the microscope's view looking upward through the eyepieces at the observer's eyeballs. The pictures shows the black, inner lens capsules and the silvery threads the capsules screw up and into. Both show something so obviously, inconceivably wrong that both the seller and the buyer overlooked it. Only by chance, did this buyer eventually recognize the problem (and his obliviousness).
Looking more closely into the second eyepiece, you can see the threads along the left and the nearest lens surface to the right:
The blue and white dots are reflections from an LED ring light. Note the yellow and brown matter in the threads around the upper left corner, and the white smudges, among the large blue dots at the right. The lens surface was originally clean, but after I held up the eyepiece and played with the diopter adjustment a few times, there were now these smudges.
Zooming in a little, and turning and tilting the lighting to reflect off the breadth of the surface, I saw there were now a good many, greasy-looking smudges:
Curious. It looked like thin strips of something had repeatedly bounced across the lens and left a trail. Hang on. Were the streaks left by debris that had fallen out of the threads, while I was playing with the eyepiece?
Then it hit me: Where is the damping grease?
The threads are worth a closer look:
Here you can see three spots of what appears to be pink grease, a few lines of clean, yellow paste and a brown, gritty residue beneath both. The pink appears viscous and the yellow has the consistency of a light, all purpose grease.
My interpretation, perhaps from a mispspent youth among story-loving geologist, is that the brown is the original damping grease, or at least something quite old, the pink is what remains of a subsequent, heavy and thorough re-greasing, and the yellow is a recent dabbing with light lithium(?) grease.
The other eyepiece is in a cleaner but similar state.
I assume all of that junk must come off: otherwise, it will slowly and awkwardly come off on its own. And then I will need to coat the threads, from end to end, with a heavy damping grease. Screwing in the well-greased lens capsules looks like it could be a pain: I can't find much purchase for a clamp.
I have some questions for those who know eyepieces, especially Zeiss eyepieces and these ones.
Does the above interpretation seem plausible?
How hard will it be to overhaul the diopter adjustments?
Will the one eyepiece's 0.1mm side-to-side play make it less useful as an eyepiece micrometer?
Thank you in advance for any and all thoughts!
