Conoscopic view

Conoscopic observation n. The study of the back focal plane of the objective by removing the eyepiece, by inserting a Bertrand lens, by examining the image at the eye-point above the eyepiece with a magnifier or by using a phase telescope is called conoscopic because the observations are associated with the cone of light furnished by the condenser and viewed by the objective (cf., orthoscopic). 

Orthoscopic observation n. The normal way of viewing an object microscopically (cf, conoscopic observation). With Kohler illumination the field diaphragm and the ocular front focal plane as well as the specimen will be in focus. 

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