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For a spherical mirror with a known aperture and working for an object at a given position, calculates the object position referred to the focal plane, the image position referred to the mirror apex, the image position referred to the focal plane, the magnification and the numerical apertures in the object and image spaces as functions of the radius of curvature, the object position referred to the mirror apex and the mirror diameter.

Note that the aperture is the plane perpendicular to the optical axis which intersection with the mirror is a circle of diameter D. Therefore, it is in general not tangent to the vertex of the mirror.