Not exit pupil, but focal point of the objective lens.
Exit pupil is the ratio of the eyepiece focal length divided by the focal ratio of the scope. Different things altogether. You use exit pupil for different aspects in selecting eyepieces for a giiven scope and its focal ratio.
Trial and error. Even if you don't have an extension tube, if rucking out the draw tube isn't enough, you can always carefully pull out the eyepiece until you achieve focus. It's just an exercise in verification for now anyway.
Alex.
|