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exit pupil
exit pupil n (Astronomy) the smallest cross section of the beam of light from the eyepiece of a telescope through which all the light from the eyepiece passes. Its diameter is equal to the ratio of the focal length of the eyepiece to the focal ratio of the telescope exit pupil
exit pupil (Ramsden disk; Ramsden circle) The image of the objective or primary mirror of a telescope formed on the eye side of the eyepiece. It is seen as a bright disk when the telescope is pointed at any extended bright surface. A convenient way to determine the magnification is to divide the telescope aperture by the diameter of the exit pupil.exit pupil[′eg·zət ‚pyü·pəl] (optics) The image of the aperture stop of an optical system formed in the image space by rays emanating from a point on the optical axis in the object space. |