Sentence:  All the rays leaving the eyepiece intersect at the <WSD>eyepoint</WSD> or exit pupil (also called Ramsden circle), and it is to this point that the observer's pupil should should be brought in order to oversee the entire field of view. The height of the eyepoint diminishes with increasing eyepiece magnification, while its diameter remains fairly constant at 1-1.5 mm. 
Meaning of the word marked with <WSD> tags:  The focal point of an optical lens.