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The small exit pupil of a 25×30 telescope and large exit pupils of 9×63 binoculars suitable for use in low light. For a telescope, the diameter of the exit pupil can be calculated by dividing the focal length of the eyepiece by the focal ratio (f-number) of the telescope. In all but the cheapest telescopes, the eyepieces are interchangeable ...
Optics showing eye relief and exit pupil 1 Real image 2 Field diaphragm 3 Eye relief 4 Exit pupil. Eye relief distance can be particularly important for eyeglass wearers and shooters. The eye of an eyeglass wearer is typically further from the eyepiece, so that user needs a longer eye relief in order to still see the entire field of view.
The eye pupil should coincide with the exit pupil, the image of the entrance pupil, which in the case of an astronomical telescope corresponds to the object glass. Eye relief typically ranges from about 2 mm to 20 mm, depending on the construction of the eyepiece.
The exit pupil is the cylinder of light exiting the eyepiece and entering the pupil of the eye; hence the lower the magnification, the larger the exit pupil. It is the image of the shrunken sky-viewing aperture of the telescope, reduced by the magnification factor, M , {\displaystyle \ M\ ,} of the eyepiece-telescope combination:
The pupil magnification of an optical system is the ratio of the diameter of the exit pupil to the diameter of the entrance pupil.The pupil magnification is used in calculations of the effective f-number, which affects a number of important elements related to optics, such as exposure, diffraction, and depth of field.
Eye relief – Eye relief is the distance from the rear eyepiece lens to the exit pupil or eye point. [15] It is the optimal distance the observer must position their eye behind the eyepiece to see a non-vignetted image. The longer the focal length of the eyepiece, the greater the eye relief.
The f-number N is given by: = where f is the focal length, and D is the diameter of the entrance pupil (effective aperture).It is customary to write f-numbers preceded by "f /", which forms a mathematical expression of the entrance pupil's diameter in terms of f and N. [1]
The exit pupil is located at infinity, and chief rays after the objective are parallel to the optical axis. An image-space telecentric lens has the exit pupil (the image of the aperture stop formed by optics after it) at infinity and produces images of the same size regardless of the distance between the lens and the film or image sensor. This ...