Abstract: An optical device for measuring the angles formed between a line-of-sight and the normal to a planar surface intersected thereby. A solid piece of optically transparent material having a relatively large index of refraction is geometrically shaped to have a planar base surface, with a reference mark theron, and a curvilinear viewing surface with scale marks to designate angular orientations. The exterior surfaces are optically polished to create mirrored surfaces for internal reflection. To accentuate contrast, the planar surface containing the reference mark is coated with a layer of contrasting opaque material. Angles are measured by placing the planar base surface of the device on the planar surface intersected by the line-of-sight and aligning the reference mark with the point of intersection. When viewed from the observation point defining the line-of-sight, an image of the reference mark appears on the scaled surface at a location representing the line-of-sight angle.