I think I can partially answer the question by giving some considerations to think about. I use these on a regular basis, being it in the field of life sciences. Judging from your post, you're an electronics repair man. From personal experience: when you have to use a stereo microscope for hours in a row, you definitly want a binocular with eyepiece tubes placed at 45°. They're more expensive, but really worth it, unless you don't mind your neck and/or your back feeling like shredded each evening... Depending on brand and model, those instruments can magnify anything between 5 x and some 150 x. In biology, and I suppose that goes for your line of work as well, magnifications above say 40 x are only rarely used. And even in an excellent instruments, the image quality deteriorates quickly above that magnification. Unless you want to pay $ 10,000 or even more. There are two types of stereo microscopes: the Greenough (GR) type and the CMO ("Common Main Objective"). Both have their (dis)advantages. The CMO has...