Title pretty much says it. I've been going through the archives looking at magnified pics and I'm wondering what you use to look at your blades. I did see Seraphim mention he used a research microscope, but what setups do you have at home?
Normally, I don't use anything. I don't want to take all the mystery out of honing. If something is required, I'll use a cheap loupe.
Its only useful for checking for edge damage, edge straightness, whether your edge is touching the stone along the entire length, alternative to the marker test, help with the marker test, microchipping... Things of that nature. Its not a sharpness test by any means.