When sharpening, many woodworkers find it useful to look at a tool's cutting edge under a microscope, although it's certainly not a necessity. A microscope lets you know what's going on during the sharpening process.
Scratch patterns, minor defects and general edge condition become apparent under magnification. This information can aid you in choosing when to switch from a coarse to a fine abrasive.
Microscopes are also useful in identifying wood species. In fact, Bruce Hoadley recommends this type of microscope in his books Understanding Wood and Identifying Wood.
Our microscope features 30X magnification, adjustable focus and a built-in light. It is just 5-1/2" long by 1-3/4" wide by 3/4" thick, so it fits comfortably in your apron pocket. It includes a vinyl case, and requires 2 AA batteries, which are not included.