The lens, or combination of lenses, at the eye end of a microscope, telescope or other optical instrument, through which the image formed by the mirror or object glass is viewed.

also known as ocular, it produces the second stage of magnification enlarging the image magnified by the objective lens. Eyepieces vary in magnification from 5x to 30x. The standard is 10x.

A (typically) 1.25" or 2" tube containing one or more lenses that is inserted in the focuser of the telescope and used to magnify the image formed by the objective lens.

A combination of lenses used to view the image formed at the focal point (or objective) of a telescope.