20 BAF Clear Rectangular Cruising Prism

This 20 BAF (Basal Area Factor) prism is a clear rectangular prism accurate to ±1% of rated BAF. This Rectangular Prism gives a narrow-sharp image for good results in dense timber. Clear glass prisms perform satisfactorily in most cruising conditions.

Prisms are an optical instrument that bends light rays to establish the critical angle. The amount of critical angle is determined by the angle to which the prism is ground. Prisms are ground to specified units of refractive displacement called diopters, to produce exact basal area factors. A diopter is a right-angled deflection of 1 centimeter per 100 centimeters of distance from the object being viewed through the prism.