Thanks, Jeff. I place the specimen inside of a ping-pong ball that I cut a hole in and I illuminate it by placing four lights against it to create a glow inside the ping-pong ball around the subject.
I fix the ISO at 200 (the lowest for this camera) and I adjust the shutter speed while looking at the histogram. The microscope objective has a depth of field of only 17-microns so not much more than a tip of a hair is is focus at any time.