The next thing I have tried is darkfield. Now the Nikon achromat condenser has its aperture hidden in a deep hole. To bring up a central stop there about would mean raising the stop som 4 or 5 cm thrugh the 18mm central bore. Possible, but not handy if one wants to change the size frequently.
My old microscope had an abbe-condenser, with filter holder just below the aperture. That looked like a better starting point for these experiments. OK, the lack of quality of that condenser was the reason to start looking for another microscope in the first place, but this is experimenting, alright?
First challenge was to make the old condenser physically fit the Labophot. I drew an adapter and took that to the 3D-printer:
It's in for parts, so I can reuse e.g. the dove tail in forthcoming projects, because the printer doesn't find it easto to print parts that grow wider with height, and the top part had to be unscrewable anyway to put the condenser inside it.
This is the result:
The stops are rings of black cardboard placed upon a 0.9 mm thick acrylic disk. here is a central pin to center the ring on the disk (in the photo, the protective foil is still on the disk):
First test show mixed results. The foreign condenser fits on the Nikon. I wonder if that expands the range of useful condensers for this microscope. In dark field mode, it appears to be that the stop must be much smaller than I thought. Even the centering pin may be too large? Also I may want to make it excentric, to enable centering.