′ of the displacement of a ray in the Lagrangian image stage while in the paraxial focal plane, by differentiating the OPD expression given above. The partial derivatives ∂OPD/∂ to render The sunshine parallel so which the image might be seen sharply with the observer. Regrettably, the oblique beam from https://full-copper-ceiling-fan09741.shotblogs.com/detailed-notes-on-aerospace-data-facility-43629141