How do you use a stadiscope?

Answer 1

A stadiscope is a device for enhancing 3D vision (and I don't know that I've had any verification that this is the right word). The only actual use I know of was in the US Army, for artillery reconnaissance, probably WWII era. I thought I had invented it until I saw one in a surplus store and later got information on it. A small version might also be especially helpful for small boats on a lake, where you want to improve 3D perception of the lake contours to determine your location.

It consists of two "periscopes". (A periscope is an assembly of two prisms or mirrors which puts the line of vision above, below or to one side of direct-eye line of vision.) One periscope (even a toy or homemade) can be used as a stadiscope, though it introduces some 3D distortion. Hold the eyepiece up to the eye, with the 'far' end pointing horizontal, away from the nose. Be sure that the objective (far end) mirror is aligned so the view through the periscope is level with the direct view of the other eye, in other words, the mirrors are on parallel planes. If you study a scene, with both eyes, one through the stadiscope, say of scattered trees 50 - 200 yards away, you'll begin to see that some trees seem much closer than others, and even near limbs stand out from others. Then add another periscope for the other eye to double enhancement and get rid of distortion. Be sure it's view also lines up with direct vision, not just with the view through the first periscope.

The Army version I've seen sits on a tripod and is combined with binocular lenses for magnification. It can be used as either periscope or stadiscope, with the periscope arms pointed up, to both sides or in-between.