Here are photographs of the setup:The high mag images are shot with Mitutoyo 10X on Raynox 150 tube lens, Canon T1i camera, illumination with diffused Jansjo LED lamps, mostly directed at a piece of white card under the specimen, with a small black card held in place as a partial darkfield stop. Vertical setup, shot through a thin layer of water with the specimen stuck into a drop of sticky water-soluble transparent "personal lubricant".
It worked out that at ISO 200, this provided an exposure time of 1/6 second. That could be an issue with mechanical first shutter curtain, especially with the "water window". But with electronic first shutter, no problem at all.
Focusing was done with the Olympus CHT block that I documented HERE and HERE. Focus stepped at 5 microns using settling time of 5 seconds, 0.3 seconds shutter pulse, 1.5 seconds after pulse, for a total of 6.8 seconds per frame. For this stack, I shot RAW+JPEG Fine, with images immediately uploaded to the laptop I was using to control the StackShot.
The bellows is a new arrangement that I currently have in prototype. It started life as an ordinary Olympus bellows. Then I cut out the middle section of the bellows rail, and mounted the two end pieces through spacers to a couple of Arca-Swiss clamps. For this application, the main advantage is that the spacers give me full freedom to rotate any of my cameras into any position I want. But I'm pretty sure that this arrangement will be easily modifiable to also do automated stepping of the rear mount by coupling that to a StackShot rail. That would have been handy a couple of times in the past.
A particular challenge when photographing in liquid is "mounting" the specimen so that it stays in the desired position to be photographed. Because of the thin water layer, tilting the stage is not an option. And because the specimen is both soft and wet, gluing or pinning it to any sort of adjustable mount didn't seem practical either. I had been told by other people that they had gotten good results with "personal lubricant", which is a mixture of water, glycerin, hydroxyethylcellulose, and some other minor ingredients. Basically it's sticky, transparent, and slowly water soluble. I had never used the trick before, but it worked great. Squeeze out a small drop of sticky stuff, use a toothpick to form it into a flat fairly thin drop, then gently press the specimen into that, position as desired, and finally flood with just enough water to cover it.
The specimen holder is a 3"x3" microscope slide with a thin section of PVC plumbing pipe glued to it.
Diffusers over the Jansjö lamps are finger ends from latex gloves.
I offer thanks to all those many people whose ideas I borrowed for this project. There's basically nothing original here, with the possible exception of the hacked bellows.
Edit: fix typo, "spaces" --> "spacers"